Apparatus and method for forming three-dimensional objects using a tilting solidification substrate

ABSTRACT

An apparatus and method for making a three-dimensional object from a solidifiable material using a linear solidification device is shown and described. The apparatus includes a solidification substrate assembly that is tiltable about a tilting axis to peel a solidification substrate from a recently formed object surface and to level the solidification substrate assembly and squeeze out accumulated solidifiable material between the solidification substrate and the recently formed object surface. Intelligent peeling and leveling may also be provided by providing a tilting parameter database that is used to adjust tilting parameters based on object geometry and/or solidifiable material properties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/506,751, filed on Oct. 6, 2014 which claims the benefit of U.S.Provisional Patent Application No. 61/942,226, filed on Feb. 20, 2014,the entirety of each of which is hereby incorporated by reference.

FIELD

The disclosure relates to an apparatus and method for manufacturingthree-dimensional objects, and more specifically, to an apparatus andmethod that forms such objects using a tilting solidification substrate.

DESCRIPTION OF THE RELATED ART

Three-dimensional rapid prototyping and manufacturing allows for quickand accurate production of components at high accuracy. Machining stepsmay be reduced or eliminated using such techniques and certaincomponents may be functionally equivalent to their regular productioncounterparts depending on the materials used for production.

The components produced may range in size from small to large parts. Themanufacture of parts may be based on various technologies includingphoto-polymer hardening using light or laser curing methods. Secondarycuring may take place with exposure to, for example, ultraviolet (UV)light. A process to convert a computer aided design (CAD) data to a datamodel suitable for rapid manufacturing may be used to produce datasuitable for constructing the component. Then, a pattern generator maybe used to construct the part. An example of a pattern generator mayinclude the use of DLP (Digital Light Processing technology) from TexasInstruments®, SXRD™ (Silicon X-tal Reflective Display), LCD (LiquidCrystal Display), LCOS (Liquid Crystal on Silicon), DMD (digital mirrordevice), MLA from JVC, SLM (Spatial light modulator) or any type ofselective light modulation system. Other examples of pattern generatorsinclude linear solidification devices that project solidification energyin a plurality of adjacent linear patterns, such as linearsolidification devices that include a laser diode in opticalcommunication with a rotating polygonal mirror. Further examples ofpattern generators include systems with a laser in optical communicationwith galvanometer mirrors that draw linear or non-linear patterns ofsolidification energy on the exposed surface of solidifiable material.

In many known techniques of making a three-dimensional object from asolidifiable resin, such as a photocurable or photopolymerizablematerial, it is necessary to create a substantially planar exposedsurface of the solidifiable resin in order to regulate the depth towhich the solidification energy penetrates and solidifies the resin. Onemethod involves placing a solidification substrate such as a plastic orglass that is translucent and/or transparent on the exposed surface ofthe resin and projecting solidification energy through the plastic orglass and into the resin. In a modified implementation, thesolidification substrate comprises a film that is either coated on theplastic or glass or is stretched over the glass or plastic withoutadhering to it. While such systems create a planar exposed resinsurface, they often also result in a bond forming between the newlyexposed surface of the object and the solidification substrate whichmust be broken prior to forming a new object layer. These systemstypically require some method or apparatus for separating the recentlyformed exposed object surface from the solidification substrate and forsubsequently introducing fresh resin between the newly formed exposedobject surface and the solidification substrate. Known techniques oftenintroduce undesirable delays in the production of objects and/orincrease the susceptibility of the part to damage, such as damage causedby forces from the surrounding resin applied against the part. Thus, aneed has arisen for an apparatus and method for making three-dimensionalobjects which addresses the foregoing issues.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will now be described, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1A is a schematic view of an apparatus for making athree-dimensional object from a solidifiable material that comprises atiltable solidification substrate assembly with the solidificationsubstrate assembly in a level configuration prior to the solidificationof the first layer of an object;

FIG. 1B is a schematic view of the apparatus of FIG. 1A in which a firstlayer of the three-dimensional object is formed on the build platform,and the solidification substrate assembly is in the level configurationof FIG. 1A;

FIG. 1C is a schematic view of the apparatus of FIG. 1A with thesolidification substrate assembly in a tilted configuration relative toa work table and the build platform following an object peelingoperation;

FIG. 1D is a schematic view of the apparatus of FIG. 1A with thesolidification substrate assembly in the tilted configuration of FIG. 1Cafter the build platform has moved away from the solidificationsubstrate assembly by one layer thickness to introduce unsolidifiedresin between the exposed object surface and the solidificationsubstrate;

FIG. 1E is a schematic view of the apparatus of FIG. 1A with thesolidification substrate assembly in the level configuration of FIG. 1Adepicting the squeezing out of resin from the space between the exposedobject surface and the solidification substrate;

FIG. 2 is a close-up schematic view of the apparatus of FIGS. 1A-1Edepicting the pressure forces applied on a pressure sensor placed on awork table;

FIG. 3 is a block diagram used to depict a controller suitable for usein the apparatus of FIGS. 1A-E in addition to various inputs to andoutputs from the controller;

FIG. 4A is a detailed first perspective view of an exemplarysolidification substrate assembly and a work table used in an apparatusfor making a three-dimensional object from a solidifiable material withthe solidification substrate assembly in a level configuration;

FIG. 4B depicts the apparatus of FIG. 4B with the solidificationsubstrate assembly in a tilted configuration;

FIG. 4C is a close-up detailed view of a portion of the apparatus ofFIGS. 4A-4B used to illustrate the connection between an actuator shaftand a load frame and the relationship between the load frame and apressure (or force) sensor on the work table when the solidificationsubstrate assembly is in a tilted configuration;

FIG. 4D is a detailed second perspective view of the apparatus of FIG.4A with the solidification substrate assembly in a tilted configuration;

FIG. 4E is a detailed perspective view of the apparatus of FIG. 4Billustrating the connection between the distal end of the actuator and aload frame latch;

FIG. 5A is an exploded perspective view of a solidification substrateframe, a load frame, and a film assembly in an unassembled condition;

FIG. 5B is a side elevation view of FIG. 5A;

FIG. 5C is a perspective view of the solidification substrate frame,load frame, and film assembly of FIGS. 5A and 5B in an assembledcondition;

FIG. 6 is a detailed perspective view of an exemplary solidificationsubstrate assembly and work table used in an apparatus for making athree-dimensional object from a solidifiable material with thesolidification substrate assembly in a level configuration;

FIG. 7 is a flow chart depicting a first method of making athree-dimensional object using an apparatus with a tiltablesolidification substrate assembly;

FIGS. 8A and 8B are a flow chart depicting a second method of making athree-dimensional object using an apparatus with a tiltablesolidification substrate assembly;

FIG. 9 is an exemplary depiction of data records from the tiltingparameter database of FIG. 3;

FIG. 10 is a detailed perspective view of an alternative exemplarysolidification substrate assembly and work table used in an apparatusfor making a three-dimensional object from a solidifiable material withthe solidification substrate assembly in a level configuration;

FIG. 11 is a view of the apparatus of FIG. 10, with the solidificationsubstrate assembly in an open configuration in which the tiltingactuators are disconnected from the work table latches;

FIG. 12A is a detailed view of a left side of the work table, loadframe, and solidification substrate of the apparatus of FIG. 10 showinga load frame bracket engaging the work table;

FIG. 12B is a detailed view of a right side of the work table, loadframe, and solidification substrate of the apparatus of FIG. 12A showinga load frame bracket engaging a load cell used to indicate the force orpressure applied by the solidification substrate assembly against thework table;

FIG. 13 is a detailed view of an actuator and actuator support of theapparatus of FIG. 10 with a modified horizontal support structure;

FIG. 14A is a graph depicting one exemplary profile of the force appliedby a motor-driven actuator to a solidification substrate assembly andthe motor load during three phases of a method of making athree-dimensional object from a solidifiable material;

FIG. 14B is a graph depicting another exemplary profile of the forceapplied by a motor-driven actuator to a solidification substrateassembly and the motor load during three phases of a method of making athree-dimensional object from a solidifiable material;

FIG. 15 is a flow chart depicting a dual-mode method of making athree-dimensional object from an apparatus comprising a tiltablesolidification substrate assembly;

FIG. 16A is a detailed perspective view of a modified version of thesolidification substrate assembly and work table of FIGS. 4A-4E in whichthe film assembly has been replaced with a removable solidificationsubstrate laminate, and the solidification substrate assembly is in anopen configuration with the tilting actuator is disconnected from thework table latch;

FIG. 16B is a top perspective view of the apparatus of FIG. 16B with thesolidification substrate assembly in a level condition during an objectsolidification operation;

FIG. 16C is an exploded assembly view of the solidification substratelaminate frame of FIG. 16A;

FIG. 16D is a perspective view of the solidification substrate laminateframe of FIG. 16C in an assembled condition;

FIG. 16E is a bottom perspective view of the solidification substratelaminate frame of FIG. 16C;

FIG. 16F is a close-up of a portion of the bottom of the solidificationsubstrate laminate frame of FIG. 16C;

FIG. 17A is a first exemplary solidification substrate laminate;

FIG. 17B is a second exemplary solidification substrate laminate; and

FIG. 17C is a third exemplary solidification substrate laminate.

Like numerals refer to like parts in the drawings.

DETAILED DESCRIPTION

The Figures illustrate examples of an apparatus and method formanufacturing a three-dimensional object from a solidifiable material.Based on the foregoing, it is to be generally understood that thenomenclature used herein is simply for convenience and the terms used todescribe the invention should be given the broadest meaning by one ofordinary skill in the art.

The apparatuses and methods described herein are generally applicable toadditive manufacturing of three-dimensional objects, such as componentsor parts (discussed herein generally as objects), but may be used beyondthat scope for alternative applications. The system and methodsgenerally include a pattern generator that applies solidification energyto a solidifiable material, such as a photohardenable resin. Thephotohardenable resin solidifies in contact with a solidificationsubstrate, i.e., a surface against which solidification occurs. Thesolidification substrate may be a rigid or semi-rigid solidificationsubstrate and/or a film.

In one aspect of the present disclosure, an apparatus for making athree-dimensional object is provided which includes a build platformthat moves along a first axis, a solidification substrate assembly, anactuator operatively connected to the solidification substrate assembly,and at least one controller operatively connected to the actuator. Thesolidification substrate assembly includes a solidification energysource, a rigid or semi-rigid solidification substrate that istransparent and/or translucent, and a film assembly. When it receives anactuator activation signal from the at least one controller, theactuator tilts the solidification substrate assembly about a secondaxis. In a first optional modification, the apparatus includes a tiltingparameter database comprising a plurality of solidifiable materialidentifiers, and a set of tilting parameters corresponding to eachsolidifiable material, wherein the set of tilting parameters includes atleast one tilting parameter. In certain optional and preferredembodiments, the apparatus does not include a peeling member thatcontacts the solidification substrate to peel it from the exposed objectsurface.

The term “tilting parameter” refers to a variable that is used tocontrol the tilting of a solidification substrate assembly. Exemplarytilting parameters include an actuator peeling distance, a minimumobject peeling travel distance, a peeling velocity, a leveling velocity,a leveling wait time, and a leveling pressure controller set point. In afurther variation of the first optional modification, at least one ofthe tilting parameters is determined based on the particularsolidifiable material from which the three-dimensional object is madeand/or object data representative of the three-dimensional object. Inone example of this variation, the at least one tilting parameter iscalculated for a plurality of layers or for each layer of the objectbased on the object data for the layer. As used herein, the phrase“minimum object peeling travel distance” refers to a minimum desiredlinear distance traveled during a tilting operation by a point of asolidification substrate that is initially in contact with a region ofan exposed object surface that is closest to the axis of tilting. Thephrase “actuator peeling distance” refers to a linear elongation of anactuator during a tilting operation. In certain examples herein, theactuator peeling distance will be a distance of travel of an actuatorshaft (either a distal end or a proximal end of the shaft) during atilting operation. In other examples, the actuator peeling distancerefers to a distance of travel of an actuator proximal housing endduring a tilting operation. The terms “peeling velocity” and “levelingvelocity” refer to the linear speed of travel of an actuator shaft (orthe speed of travel of the actuator housing) during tilting operationsconducted to peel a solidified object from a solidification substrateand to return the solidification substrate to a level configuration,respectively.

In another aspect of the present disclosure, an apparatus for making athree-dimensional object from a solidifiable material is provided whichcomprises a linear solidification device that is movable along a firstaxis while progressively supplying solidification energy along a secondaxis. The apparatus further comprises a rigid or semi-rigidsolidification substrate that is transparent and/or translucent, anactuator operatively connected to the rigid or semi-rigid solidificationsubstrate and operable to tilt the substrate about the second axis, anda build platform movable along a third axis. In an optionalmodification, the solidification substrate assembly also includes a filmassembly, and the actuator is operatively connected to the film assemblyand is operable to tilt the film assembly about the second axis. In thesame optional modification or in a different one, the linearsolidification device and the rigid or semi-rigid solidificationsubstrate comprise a solidification substrate assembly, and the actuatoris operatively connected to the solidification substrate assembly andoperable to tilt the solidification substrate assembly about the secondaxis. In certain optional and preferred examples, the apparatus does notinclude a peeling member that contacts the solidification substrate topeel it from the exposed object surface.

In a further optional modification, at least one controller isoperatively connected to the actuator. The at least one controllercomprises a processor and a non-transitory computer readable mediumhaving computer executable instructions stored thereon. When thecomputer executable instructions are executed by the processor, the atleast one controller generates an actuator activation signal, and theactuator tilts the solidification substrate in response to the actuatoractivation signal. In the same or in another optional modification, theapparatus includes a tilting parameter database comprising a pluralityof solidifiable material identifiers, and a plurality of sets of tiltingparameters, each set corresponding to a solidifiable materialidentifier, wherein each set of tilting parameters includes at least onetilting parameter. In a further variation of the first optionalmodification, at least one of the tilting parameters is determined basedon the particular solidifiable material from which the three-dimensionalobject is made and/or object data representative of thethree-dimensional object. In one example of this variation, the at leastone tilting parameter is calculated for a plurality of layers or foreach layer of the object based on the object data for the layer.

In a further aspect of the present disclosure, a method of making athree-dimensional object from a solidifiable material is provided whichcomprises providing a layer of the solidifiable material having anexposed surface adjacent a rigid or semi-rigid solidification substrate,wherein the rigid or semi-rigid solidification substrate is transparentand/or translucent. The method further comprises moving a linearsolidification device along a first axis, progressively exposingportions of the layer of solidifiable material to solidification energyfrom the linear solidification device along a second axis as the linearsolidification device moves along the first axis, and tilting thesolidification substrate about the second axis. In one optionalmodification, the step of tilting the solidification substrate about thesecond axis comprises tilting the solidification substrate away from thebuild platform about the second axis, and moving the build platform in adirection away from the solidification substrate by a desired layerthickness. In the same or another optional modification, the step oftilting the solidification substrate about the second axis comprisesselecting at least one tilting parameter based on the solidifiablematerial and tilting the solidification substrate about the second axisin accordance with the at least one tilting parameter. The tiltingparameter may also be selected based on the object data in addition toor instead of selecting it based on the solidifiable material. In oneexample of this variation, the at least one tilting parameter iscalculated for a plurality of layers or for each layer of the objectbased on the object data for the layer. In certain optional andpreferred examples, the method does not comprise traversing a peelingmember to contact the solidification substrate and peel it from theexposed object surface.

In yet another aspect of the present disclosure, a method of making athree-dimensional object from a solidifiable material is provided whichcomprises solidifying a portion of the solidifiable material to createan exposed solidified object surface in contact with a solidificationsubstrate, and tilting the solidification substrate about a first axisin accordance with at least one tilting parameter, wherein the at leastone tilting parameter is based on at least one of object datarepresentative of the three-dimensional object and the solidifiablematerial. In a first optional variation, the at least one tiltingparameter is based on both object data representative of the object andthe solidifiable material. In one example, the at least one tiltingparameter for a given layer is determined based on the exposed objectarea defined by the object data for the layer. In another example, afirst tilting parameter is provided which comprises a minimum objectpeeling travel distance, and a second tilting parameter which comprisesan actuator peeling distance (i.e., a distance of extension orretraction by a tilting actuator used to carry out the tiltingoperation) is determined based on object data and/or the minimum objectpeeling travel distance. In certain optional and preferred examples, themethod does not comprise traversing a peeling member to contact thesolidification substrate and peel it from the exposed object surface. Inother optional and preferred examples, the solidification substrate isrigid or semi-rigid and is transparent and/or translucent. In optionaland preferred embodiments, the solidification substrate is a transparentand/or translucent resilient layer or protective film.

In an additional aspect of the present disclosure, a method of making athree-dimensional object from a solidifiable material is provided whichcomprises solidifying a first layer of the solidifiable material in afirst pattern corresponding to a first portion of the three-dimensionalobject to form a first solidified exposed object surface in contact witha solidification substrate, wherein the first layer of the solidifiablematerial is located between a build platform and the solidificationsubstrate along a build axis. The method also comprises first tiltingthe solidification substrate about a tilting axis in a direction awayfrom the build platform, moving the build platform away from thesolidification substrate within a volume of the solidifiable material toprovide a second layer of solidifiable material between the solidifiedexposed object surface and the solidification substrate, second tiltingthe solidification substrate about the tilting axis in a directiontoward the build platform; and solidifying the second layer of thesolidifiable material in a second pattern corresponding to a secondportion of the three-dimensional object. In certain optional andpreferred examples, the solidification substrate is transparent and/ortranslucent and is a resilient layer, a film, or is rigid or semi-rigid.In other optional and preferred examples, a tilting parameter databasecomprising sets of tilting parameters stored in association withsolidifiable material identifiers is provided, and a tilting operationis carried out based on a tilting parameter from the tilting parameterdatabase. In further optional and preferred examples, the solidificationsubstrate assembly includes a source of solidification energy. Inadditional optional and preferred examples, the method does not comprisetraversing a peeling member to contact the solidification substrate andpeel it from the exposed object surface.

In certain examples, the apparatuses and methods described hereinbeneficially increase the speed of a method of making athree-dimensional object while preserving the integrity of the object.As described further below, in certain examples, the tilting apparatusesand methods also tailor the tilting process to object properties, suchas exposed surface area and/or the location of the object relative tothe axis of tilting, which may vary on a layer by layer basis so thatonly the required amount of tilting to affect part separation or toprovide a stable layer of solidifiable material is performed.

In still another aspect of the present disclosure, a method of making athree-dimensional object is provided which comprises solidifying a layerof solidifiable material in contact with a solidification substratelaminate to create a portion of a three-dimensional object having anexposed object surface adhered to an object-contacting surface of thesolidification substrate laminate. The three-dimensional object isdisposed on a build platform, and the step of solidifying thesolidifiable material comprises projecting solidification energy throughan open top of a solidifiable material container that contains the layerof solidifiable material and which has a closed bottom. The methodfurther comprises tilting the solidification substrate laminate about atilting axis in a direction away from the build platform to separate thethree-dimensional object from the solidification substrate laminate,lowering the build platform such that a next layer of solidifiablematerial flows over the exposed object surface, and tilting thesolidification substrate laminate about the tilting axis in a directiontoward the build platform. In certain examples, the solidificationsubstrate laminate comprises a rigid or semi-rigid solidificationsubstrate that is transparent and/or translucent and either or both of aresilient layer and a protective film.

In a further aspect of the present disclosure, an apparatus is providedwhich comprises a source of solidification energy, a solidifiablematerial container having a closed bottom and an open top, a buildplatform movable along a build axis and having an object build surfacethat faces the open top and the source of solidification energy, asolidification substrate assembly comprising one selected from a filmassembly and a solidification substrate laminate, an at least oneactuator operatively connected to the solidification substrate assemblywhich is operable to tilt the solidification substrate assembly about atilting axis. In certain examples, the solidification substrate assemblycomprises the solidification substrate laminate, and the solidificationsubstrate laminate comprises a rigid or semi-rigid solidificationsubstrate that is transparent and/or translucent, and either or both ofa resilient layer and a protective film.

As discussed herein, a solidifiable material is a material that whensubjected to energy, wholly or partially hardens. This reaction tosolidification or partial solidification may be used as the basis forconstructing the three-dimensional object. Examples of a solidifiablematerial may include a polymerizable or cross-linkable material, aphotopolymer, a photo powder, a photo paste, or a photosensitivecomposite that contains any kind of ceramic based powder such asaluminum oxide or zirconium oxide or ytteria stabilized zirconium oxide,a curable silicone composition, silica based nano-particles ornano-composites. The solidifiable material may further include fillers.Moreover, the solidifiable material my take on a final form (e.g., afterexposure to the electromagnetic radiation) that may vary fromsemi-solids, solids, waxes, and crystalline solids. In one embodiment ofa photopolymer paste solidifiable material, a viscosity of between 10000cP (centipoises) and 150000 cp is preferred.

When discussing a photopolymerizable, photocurable, or solidifiablematerial, any material is meant, possibly comprising a resin andoptionally further components, which is solidifiable by means of supplyof stimulating energy such as electromagnetic radiation. Suitably, amaterial that is polymerizable and/or cross-linkable (i.e., curable) byelectromagnetic radiation (common wavelengths in use today include UVradiation and/or visible light) can be used as such material. In anexample, a material comprising a resin formed from at least oneethylenically unsaturated compound (including but not limited to(meth)acrylate monomers and polymers) and/or at least one epoxygroup-containing compound may be used. Suitable other components of thesolidifiable material include, for example, inorganic and/or organicfillers, coloring substances, viscose-controlling agents, etc., but arenot limited thereto.

When photopolymers are used as the solidifiable material, aphotoinitiator is typically provided. The photoinitiator absorbs lightand generates free radicals which start the polymerization and/orcrosslinking process. Suitable types of photoinitiators includemetallocenes, 1,2 di-ketones, acylphosphine oxides,benzyldimethyl-ketals, α-amino ketones, and α-hydroxy ketones. Examplesof suitable metallocenes include Bis (eta 5-2, 4-cyclopenadien-1-yl) Bis[2,6-difluoro-3-(1H-pyrrol-1-yl) phenyl] titanium, such as Irgacure 784,which is supplied by Ciba Specialty chemicals. Examples of suitable 1,2di-ketones include quinones such as camphorquinone. Examples of suitableacylphosphine oxides include bis acyl phosphine oxide (BAPO), which issupplied under the name Irgacure 819, and mono acyl phosphine oxide(MAPO) which is supplied under the name Darocur® TPO. Both Irgacure 819and Darocur® TPO are supplied by Ciba Specialty Chemicals. Examples ofsuitable benzyldimethyl ketals include alpha,alpha-dimethoxy-alpha-phenylacetophenone, which is supplied under thename Irgacure 651. Suitable α-amino ketones include2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl) phenyl]-1-butanone,which is supplied under the name Irgacure 369. Suitable α-hydroxyketones include 1-hydroxy-cyclohexyl-phenyl-ketone, which is suppliedunder the name Irgacure 184 and a 50-50 (by weight) mixture of1-hydroxy-cyclohexyl-phenyl-ketone and benzophenone, which is suppliedunder the name Irgacure 500.

Referring now to FIGS. 1A-1E, an apparatus 40 for making athree-dimensional object from a solidifiable material is depicted. Theapparatus 40 includes a housing 42 in which a container 44 is disposed.The container 44 has a closed bottom 45 and an open top 47 and holds avolume of solidifiable material 50, which is preferably aphotohardenable liquid or paste that solidifies upon exposure tosolidification energy of an appropriate wavelength and intensity for asufficient period of time. A three-dimensional object 78 (FIG. 1B) isprogressively built upward on build platform 46 in the positive build(z) axis direction by supplying solidification energy from the linearsolidification device 62 to the solidifiable material 50 during anobject solidification operation. The solidification energy is suppliedin geometric patterns that correspond to object data, causing thesolidifiable material to solidify in a shape corresponding to the objectdata.

At least one controller (not shown in FIGS. 1A-1E) is provided toselectively activate a solidification energy source in the linearsolidification device 62 and to selectively energize a linearsolidification device motor (not shown) that is operable to traverse thelinear solidification device 62 along a travel (x) axis. Examples oflinear solidification devices are described in FIGS. 3, 4, and 5A-5D ofApplicant's co-pending U.S. patent application Ser. No. 13/534,638,filed on Jun. 27, 2012 and the corresponding text, including atparagraphs 60-79 and 86-104, the contents of which are herebyincorporated by reference. Exemplary pattern generators other thanlinear solidification devices which may be used include DLP (DigitalLight Processing technology) from Texas Instruments®, SXRD™ (SiliconX-tal Reflective Display), LCD (Liquid Crystal Display), LCOS (LiquidCrystal on Silicon), DMD (digital mirror device), J-ILA from JVC, SLM(Spatial light modulator) or any type of selective light modulationsystem. Pattern generators that “draw” laser energy in two-dimensionallyvarying patterns across an exposed surface of solidifiable material mayalso be used, such as those that comprise a laser in opticalcommunication with x-y galvanometer mirrors. The linear solidificationdevice 62 projects solidification energy through the open top 47 ofsolidifiable material container 44 as well as through rigid orsemi-rigid solidification substrate 58 and film 60.

The object 78 is built on an upward facing surface (or object buildsurface) 48 of the build platform 46. Object 78 includes a buildplatform contacting surface 80 that rests on (and typically is adheredto) the object build surface 48 of build platform 46. The build platformcontacting surface 80 typically comprises discrete, removable supports.The object build surface 48 faces the open top 47 of solidifiablematerial container 44 and linear solidification device 62. Avertically-movable shaft 52 is movable within the housing 42 to adjustthe build (z) axis position of the build platform 46 relative to thework table 64. The bottom of the vertically-movable shaft 52 iscontained within a bottom portion of the housing 42 which is not shownfor ease of illustration. A build platform motor (not shown) is providedand is operable to move the build platform 46 along the build (z) axis.At least one controller (not shown) is operatively connected to thebuild platform motor to selectively operate it in accordance withcomputer executable instructions stored in the non-transitory memory ofthe at least one controller and executed by the processor of the atleast one controller. In certain examples herein, when executed by theprocessor, the computer executable instructions cause the build platform46 to move downward along the build (z) axis by a defined layerthickness Δz following the solidification of a layer of the solidifiablematerial.

The apparatus 40 also includes a solidification substrate assembly 57,which in the depicted embodiment includes a rigid or semi-rigidsolidification substrate 58, a film 60, and a load frame 56. The film 60has an object-contacting surface 61 which faces the closed bottom 45 ofsolidifiable material container 44. In the example of FIGS. 1A-1E, thesolidification substrate assembly 57 also comprises the linearsolidification device 62. The rigid or semi-rigid solidificationsubstrate 58 is preferably transparent and/or translucent tosolidification energy supplied by a source of solidification energy. Inthe example of FIGS. 1A-1E, the source of solidification energy isprovided in a linear solidification device 62. Although not depicted inFIGS. 1A-1E, the linear solidification device 62 is attached to the loadframe 56 via a pair of linear rails spaced apart from one another in they-axis direction and along which a support member attached to the linearsolidification device 62 slidably translates in the x-axis direction. Asfurther illustrated in the examples of FIGS. 4A-6, the rigid orsemi-rigid solidification substrate 58 may be provided in a separateframe that attaches to the load frame 56, and the film 60 may beprovided in a film assembly that attaches to the load frame 56 or to aframe holding the rigid or semi-rigid solidification substrate 58. Ineither event, the rigid or semi-rigid solidification substrate 58 andfilm 60 are directly or indirectly attached to the load frame 56 andmovable therewith. In the example of FIGS. 1A-1E, film 60 is not bondedor adhered to the rigid or semi-rigid solidification substrate 58 butmay closely contact the substrate 58. However, in other examples, and asdescribed below with reference to FIGS. 16A-16F and 17A-17C, instead ofusing a rigid or semi-rigid solidification substrate 58 and a separatefilm 60, a solidification substrate laminate 298 may be used. Thesolidification substrate laminate 298 may comprise a resilient layerand/or a protective film bonded to rigid or semi-rigid solidificationsubstrate 58 to define an integral, layered structure. In that case,solidification substrate laminate 298 includes an object contactingsurface 301 that faces the closed bottom 45 of solidifiable materialcontainer 44.

As indicated previously, solidifiable material 50, such as aphotohardenable resin, is provided under substantially rigid orsemi-rigid substrate 58 to receive solidification energy transmittedthrough substrate 58. Solidification substrate 58 is generally rigid orsemi-rigid and substantially permeable to the energy supplied by linearsolidification device 62. In certain examples, it is preferred that theenergy from linear solidification device 62 pass through solidificationsubstrate 58 without a significant diminution in transmitted energy or asignificant alteration of the energy spectrum transmitted to thesolidification material 50 relative to the spectrum that is incident tothe upper surface of solidification substrate 58. In the case where theenergy from linear solidification device 62 is light (includingnon-visible light such as UV light), solidification substrate 58 ispreferably substantially transparent and/or translucent to thewavelength(s) of light supplied by linear solidification device 62.

One example of a rigid or semi-rigid solidification substrate 58 is atranslucent float glass. Another example is a translucent plastic. Avariety of different float glasses and plastics may be used. Exemplaryplastics that may be used include transparent and/or translucent acrylicplastics supplied by Evonik under the name Acrylite®. The term“translucent” is meant to indicate that substrate 58 is capable oftransmitting the light wavelengths (including non-visible light such asUV light) necessary to solidify the solidifiable material and that theintensity of such wavelengths is not significantly altered as the lightpasses through substrate 58. In the case of photopolymer solidifiablematerials, a photoinitiator is commonly provided to start thepolymerization/cross-linking process. Photoinitiators will have anabsorption spectrum based on their concentration in the photopolymer.That spectrum corresponds to the wavelengths that must pass throughsolidification substrate 58 and which must be absorbed by thephotoinitiator to initiate solidification. In one example whereinsolidification energy source in the linear solidification device 62 is ablue laser light diode, Irgacure 819 and Irgacure 714 photoinitiatorsmay preferably be used.

Film 60 is preferably transparent and/or translucent and is ahomopolymer or copolymer formed from ethylenically unsaturated,halogenated monomers. Fluoropolymers are preferred. Examples of suitablematerials for protective film 60 include polyvinylidene fluoride (PVDF),ethylenchlorotrifluoroethylene (ECTFE), ethylenetetrafluoroethylene(ETFE), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), andmodified fluoroalkoxy (a copolymer of tetrafluoroethylene andperfluoromethylvinylether, also known as MFA). Examples of suitable film60 materials include PVDF films sold under the Kynar® name by Arkema,ECTFE films sold under the Halar® name by SolvaySolexis, ETFE films soldunder the Tefzel® name by DuPont, PFA films sold under the Teflon®-PFAname by DuPont, and MFA films sold under the name Nowofol. MFA andTeflon® films are preferred

The solidification substrate assembly 57 is attached to a work table 64via a pair of hinges 74 a and 74 b (only hinge 74 b is visible in FIGS.1A-1E) which are both located on a first side 72 a of the load frame 56and spaced apart from one another along the y-axis. The hinges 74 a and74 b are also attached to the work table 64 at a first side 65 a of thework table 64. The hinges 74 a and 74 b define an axis of tilting orrotation for the solidification substrate assembly 57. Thus, during atilting operation, the solidification substrate assembly 57 tilts aboutthe axis defined by hinges 74 a and 74 b, which is parallel to they-axis in the figures. In the example of FIGS. 4A-4E, solidificationsubstrate assembly 57 also comprises linear solidification device 62.

The apparatus 40 includes a tilting actuator 66 that is operativelyconnected to the solidification substrate assembly 57. Actuator 66 has ahousing 67 with a proximal end 73 and a shaft 68 with a distal end 70.The shaft 68 has a proximal end that is located in the housing 67 andwhich is not visible in the figures. In FIGS. 1A-1E the distal end 70 ofactuator shaft 68 is connected to the left-side 72 b of load frame 56 ofthe solidification substrate assembly 57. Right-side 72 a of load frame56 is spaced apart from left-side 72 b along the x-axis. A bracket 76 isprovided to connect the actuator 66 to the left-side 65 b of the worktable 64. Right-side 65 a of work table 64 is spaced apart fromleft-hand side 65 b along the x-axis. The position of actuator housing67 is fixed relative to bracket 76 and the work table 64. However, theactuator shaft distal end 70 is movable relative to the work table 64and the actuator housing 67 along the build (z) axis. The actuator 66has an extended configuration (FIGS. 1C and 1D) and a retractedconfiguration (FIGS. 1A-B, and 1E). The length of actuator 66—as definedby the distance between the proximal actuator end 73 and the distalshaft end 70 along an axis defined by the actuator shaft 68 length—islonger in the extended configuration than in the retractedconfiguration. The length axis of actuator shaft 68 is generallyparallel to the build (z) axis and is substantially parallel to thebuild (z) axis when the solidification substrate assembly 57 is in alevel configuration (FIGS. 1A-1B, and 1E). However, the actuator shaft68 length axis will tilt relative to the build (z) axis during asolidification substrate assembly 57 tilting operation because thesolidification substrate assembly 57 traverses a circular path whenviewed along the y-axis during a tilting operation. The actuator shaft68 will exhibit its maximum degree of tilt relative to the build (z)axis when the shaft distal end 70 reaches its fully extended position.

Suitable actuators 66 include pneumatic actuators and linear actuatorsthat are electromechanical. One suitable electromechanical linearactuator is a 100 pound maximum lift linear actuator supplied by EzzyLift. The actuator has a two inch (2) stroke (i.e., the maximumdisplacement of the distal end 70 from a fully retracted to a fullyextended configuration is two (2) inches (50.8 mm)). The Ezzy Liftactuator has a maximum actuator travel speed (which is equivalent to apeeling velocity tilting parameter described below) of 12.8 mm/sec.

The actuator 66 is adjustable from the retracted configuration to theextended configuration to tilt the solidification substrate assembly 57about the tilting axis defined by hinges 74 a and 74 b (not shown). Inthe example of FIGS. 1A-1E, the actuator 66 is positioned with its shaft68 underneath the load frame 56 along the build (z) axis. In FIG. 1A,the actuator 66 is in the retracted configuration in which distal shaftend 70 is in a first retracted position along the build (z) axis that isrelatively closer to the build platform 46 and to the proximal actuatorend 73 along the build (z) axis than when the actuator 66 is in theextended configuration (FIGS. 1C-1D) in which distal shaft end 70 is ina second extended position along the build (z) axis. Thus, in theexample of FIGS. 1A-1E, the distal shaft end 70 has an extended positionin which it is spaced apart farther from both build platform 46 andactuator 66 along the build (z) axis.

The actuator 66 is adjustable from the retracted configuration of FIGS.1A-1B to the extended configuration of FIGS. 1C and 1D to cause thesolidification substrate assembly 57 to tilt about the tilting axis in adirection away from the build platform 46. The tilting of thesolidification substrate assembly 57 away from build platform 46 may beused to carry out an object peeling operation as will be describedfurther herein.

As FIGS. 1C and 1D indicate, the extension of the actuator shaft 68 froma retracted configuration to an extended configuration causes thesolidification substrate assembly 57, including linear solidificationdevice, the load frame 56, rigid or semi-rigid solidification substrate58 and film 60, to tilt about the tilting axis defined by the hinges 74a (not shown) and 74 b. However, as discussed further below withreference to the apparatus of FIG. 6, the actuator 66 may be configureddifferently so that the retraction of shaft 68 causes the solidificationsubstrate assembly 57 to tilt away from the build platform 46. In thatcase, when the actuator shaft distal end 70 is in a first fullyretracted position, the distal end 70 is spaced apart from the buildplatform 46 along the build (z) axis by a distance that is greater thanthe build (z) axis distance by which the distal shaft end 70 is spacedapart from the build platform 46 when actuator shaft distal end 70 is ina second fully extended position. In yet another alternative, and asdiscussed further below with respect to the example of FIGS. 10-13, thedistal end 70 of the actuator 66 may be connected to a stationarysurface such as work table 64 such that when the actuator 66 is in anextended configuration, the proximal end 73 moves away from the distalshaft end 70 and the build platform 46 and when the actuator 66 is aretracted configuration, the proximal end 73 moves toward the distalshaft end 70 and the build platform 46. In this configuration, theposition of the proximal actuator end 73 relative to the tiltablesolidification substrate assembly 57 remains fixed but is movablerelative to the work table 64.

In certain known systems, following the solidification of a layer ofsolidifiable material, as depicted in FIG. 1B, the build platform 46will descend by whatever distance is required to separate the exposedobject surface 82 from the film 60 or rigid or semi-rigid solidificationsubstrate 58 if no film is present. In such systems, the full peelingforce is applied simultaneously across the entire exposed object surface82 area of the object 78. The object 78 tends to become susceptible tobreakage if the force per unit area of the exposed object surface 82increases beyond a certain threshold. Therefore, in many known systems,the build platform 46 must be pulled away from the film 60 at a reducedspeed to reduce the force per unit area and preserve the integrity ofthe object 78. In contrast, the peeling process carried out by theapparatus of FIGS. 1A-1E and the other apparatuses described hereinyields a dynamically varying force profile along the x-axis and reducesthe force per unit area during peeling operations relative to processesin which an entire layer is separated by a vertical force. Also, inpreferred implementations of the apparatus 40 of FIGS. 1A-1E, peelingmay be completed before the build platform 46 moves. Thus, the peelingprocess is not dependent on the build platform 46 movement and does notlimit the speed of build platform 46 movement.

FIG. 1C depicts the apparatus 40 with the solidification substrateassembly 57 in a peeled and tilted configuration in which the rigid orsemi-rigid solidification substrate 58 and film 60 have fully separatedfrom the exposed object surface 82. In FIG. 1C, actuator 66 is in anextended configuration. In some implementations, peeling operations maybe carried out by extending the actuator shaft 68 by a fixed amount (theactuator peeling distance, which is shown as Δa in FIGS. 1A-1E)following the formation of each object layer. However, in otherimplementations, the actuator peeling distance may be varied based onthe object data for the just-solidified layer. The location of theexposed object surface 82 along the x-axis for any given object layerwill generally dictate the extent to which the actuator shaft 68 must beextended to fully peel the exposed object surface 82 from the film 60.Thus, in these other implementations, the actuator peeling distance Δais adjusted for one or more layers of the three-dimensional object toeffect the minimum degree of peeling required given the x-axisdimensions of the most recently formed object layer. Because of thehinged connection between the solidification substrate assembly's loadframe 56 and the work table 64, the solidification substrate assembly 57undergoes a circular motion (when viewed along the y-axis) during apeeling operation. As a result, those points of film 60 or substrate 58which are in contact with locations on the exposed object surface 82that are relatively farther (along the x-axis) from the tilting axis(defined by hinges 74 a and 74 b) will travel a greater distance duringa tilting operation than will points of film 60 or substrate 58 that arein contact with locations on the exposed object surface 82 that arerelatively closer (along the x-axis) to the tilting axis. Therefore, incertain implementations, the actuator peeling distance Δa is adjusted sothat a portion on the exposed object surface 82 that is in contact withfilm 60 and which is closest (along the x-axis) to the tilting axis(i.e., closest to the hinges 74 a and 74 b) will travel during an objectpeeling operation from a starting location to an ending location thatdefines a linear travel vector having a length equal to the minimumobject peeling travel distance Δg. In such implementations, as thex-axis location of the portion of the exposed object surface 82 that isclosest to the tilting axis varies, so will the actuator peelingdistance Δa. This technique helps ensure that only the necessary amountof peeling is performed, which in turn reduces the time required tobuild three-dimensional parts. In FIG. 1C, the minimum object peelingdistance Δg is shown as being a vertical spacing. However, in practiceit is a vector with a variable direction which may or may not beparallel to the build (z) axis. Also, the actuator shaft 68 is shown asextending in a direction parallel to the build (z) axis. However, due tothe hinged connection of the load frame 56 to the work table 64, theactuator distal end 70 will traverse a generally circular path duringtilting operations, and thus, the shaft 68 may tilt away from the build(z) axis.

In the example of FIG. 1C, the exposed surface 51 of the solidifiablematerial 50 is beneath the fully retracted position of the actuatordistal end 70 and the hinges 74 a and 74 b along the build (z) axis. Inthe figures, the difference between the vertical (z-axis) spacingbetween the actuator shaft distal end 70 and the exposed solidifiablematerial surface 51 on the one hand and the actuator shaft distal end 70and hinges 74 a and 74 b on the one hand is identified as Δf. With thisconfiguration, the rigid or semi-rigid solidification substrate 58 maybe positioned beneath the open top of the solidifiable materialcontainer 44. In certain examples, the actuator peeling distance Δa maybe calculated from the minimum object peeling travel distance Δg, usingthe following relationship:

$\begin{matrix}{{\Delta\; a} = \frac{\left( {{Lt} \times \Delta\; g} \right)}{\sqrt{\left( {{Lp}^{2} + {\Delta\; f^{2}}} \right)}}} & (1)\end{matrix}$

-   -   wherein, Δa=actuator peeling distance (mm);        -   Lt=distance along the x-axis from actuator to hinges (mm);        -   Lp=shortest distance along the x-axis from exposed object            surface to hinges (mm);        -   Δf=difference between (1) the z-axis distance between the            actuator shaft distal end 70 and the exposed solidifiable            material surface 51 and (2) the z-axis distance between the            actuator shaft distal end and hinges 74 a and 74 b (mm).

Sensors may be provided to indicate the completion of an object peelingoperation. In one example, a limit switch may be provided whichgenerates a signal when the actuator distal end 70 reaches itsfully-extended, end of travel position along the build (z) axis. Whenfixed actuator peeling distances Δa are used carry out object peelingoperations, the limit switch may be operatively connected to acontroller and used by the controller to sequence subsequent operationsfollowing the completion of an object peeling operation.

Following the solidification of an object layer, the build platform 46descends by a desired layer thickness Δz as shown in FIG. 1D. The buildplatform 46 may descend during the object peeling operation or followingit. In preferred examples, the build platform 46 descends following thecompletion of the object peeling operation. The movement of the buildplatform 46 allows unsolidified solidifiable material 50 to flow intothe region above the exposed object surface 82 and create a new exposedsolidifiable material surface 51. In FIG. 1D, the exposed object surface82 is spaced apart from the exposed solidifiable material surface 51 bythe desired layer thickness Δz.

Prior to solidifying a new layer of solidifiable material 50, thesolidification substrate assembly 57 is tilted into a levelconfiguration by carrying out a leveling operation as shown in FIGS. 1Dto 1E. To carry out the leveling operation, the distal end 70 of theactuator shaft 68 is retracted along the build (z) axis to itsfully-retracted position, as shown in FIG. 1E. During the levelingoperation, the rigid or semi-rigid solidification substrate 58 and film60 apply a pressure in the negative build (z) axis direction against thesolidifiable material 50 that is located in the region between theexposed object surface 82 and the film 60. This pressure has the effectof “squeezing” out material trapped in this region as shown by thecurved arrows in FIG. 1E.

During the squeezing process, the solidifiable material experiencessmall localized waves and other transient hydrodynamic phenomena. Thus,in general, it is desirable to ensure that the squeezing operation iscomplete before the linear solidification device 62 begins solidifyingthe next layer to avoid distortions in the resulting three-dimensionalobject. One technique of ensuring that squeezing is complete is to waituntil the expiration of a “leveling wait time” after the solidificationsubstrate assembly 57 is in the level configuration of FIG. 1E. Incertain examples herein, leveling wait times of no more than about 60seconds are preferred, and leveling wait times of no more than about 45seconds, and no more than about 35 seconds, are more preferred and evenmore preferred respectively. At the same time, leveling wait times of atleast about 2 seconds, at least about 5 seconds, and at least about 8seconds are preferred, more preferred, and especially preferred,respectively. In one example, a leveling wait time of about 10 secondsis used.

As an alternative to using a leveling wait time, a pressure or forcesensor may also be provided and used to determine when a squeezingoperation is complete. The pressure sensor is preferably directly orindirectly indicative of the fluid pressure exerted by solidifiablematerial 50 against the film 60 and rigid or semi-rigid solidificationsubstrate 58. During a squeezing operation, this pressure (which has adirection in the positive or upward build (z) axis direction) willdecrease until squeezing is complete. An exaggerated schematic view ofone possible pressure sensor configuration is depicted in FIG. 2.Pressure sensor 86 comprises a load cell attached to the left-hand side65 b of work table 64 so as to be spaced apart from the hinges 74 a and74 b along the x-axis. A load bracket 84 is attached to the load frame56 at the load frame left hand side 72 b and overlaps with the pressuresensor 86 along the x-axis. The load bracket 84 applies a negative(downward) build (z) axis force against the pressure sensor 86. Atequilibrium (i.e., when no squeezing is occurring) the weight of thesolidification substrate assembly 57 will exert a non-zero referenceforce in the negative build (z) axis direction against the load cellwhich will be offset to some extent by the pressure exerted by thesolidifiable material 50 against the film 60 and rigid or semi-rigidsolidification substrate 58. Thus, the sensor 86 will produce anon-zero, equilibrium pressure reading when no squeezing is occurring.

With the pressure sensor 86 configured as shown, during a squeezingoperation, the positive build (z) axis force applied by the solidifiablematerial 50 against the film 60 and rigid or semi-rigid solidificationsubstrate 58 will provide a net force exerted against the pressuresensor 86 that is lower than the equilibrium force exerted against thesensor 86 when no squeezing is occurring. As squeezing continues, thepositive build (z) axis force applied by the solidifiable material 50will decrease, causing the pressure sensor 86 reading to increase towardthe equilibrium, non-zero reference pressure, which indicates thatsqueezing is complete. In addition to using the pressure value itself,the change in the pressure value with respect to time (dP/dt) may beused as an indication that squeezing is complete by comparing the changewith a specified threshold change. In certain examples, the non-zeroreference pressure (or reference value of dP/dt) is a tilting parameterand may be varied based on the particular solidifiable material 50 thatis used. In general, more highly viscous solidifiable materials willexert a greater upward force against the film 60 and rigid or semi-rigidsolidification substrate 58 at equilibrium, and for such materials arerelatively higher non-zero reference pressure is selected as compared tolower viscosity materials.

In certain exemplary implementations, the actuator 66 applies a constantforce against the solidification substrate assembly 57 during an objectpeeling operation. In other exemplary implementations, the actuator 66applies a constant force against the solidification substrate assembly57 during a leveling operation. In further exemplary implementations,the actuator 66 applies a constant force against the solidificationsubstrate assembly 57 during both an object peeling operation and aleveling operation (albeit in opposite directions). In a preferredmethod, the same constant force is applied during an object peeling anda leveling operation (albeit in opposite directions), and the constantforce (in the negative build (z) axis direction) remains after thesolidification substrate assembly 57 is level, which stabilizes theassembly against the upward pressure of the solidifiable material 50.

In certain implementations of the apparatus 40 of FIGS. 1A-1E, it hasbeen found that during the first several layers of an objectsolidification operation, it may not be possible to obtain sufficientsolidifiable material 50 above the exposed object surface 82 to developa new layer of solidifiable material 50 of the desired layer thicknessΔz. Without wishing to be bound by any theory, it is believed thatinsufficient material is available above the upward facing surface 48 ofthe build platform 46 during the formation of the first several objectlayers to sufficiently cover the build platform 46 and the object 78because of the close proximity of build platform 46 to the exposedsurface 51 of the solidifiable material 50. Thus, in a “deep dipping”variation of the technique described in the preceding paragraph, duringthe formation of an initial set of object layers, the build platform 46is dipped in the negative build (z) axis direction by an amount greaterthan the desired layer thickness Δz and is subsequently elevated in thepositive build (z) axis direction until the exposed object surface 82 isspaced apart from the exposed solidifiable material surface 51 by thedesired layer thickness Δz. In preferred implementations of thisvariation, the deep dipping step is carried out during the formation ofat least layer 2, more preferably during layers 2-3, still morepreferably during layers 2-4, even more preferably during layers 2-5,still more preferably during layers 2-6, yet more preferably duringlayers 2-7, even more preferably during layers 2-8, and still morepreferably during layers 2-9, and yet more preferably during layers2-10. The deep dipping process is preferably carried out for no morethan the first 30 layers, even more preferably no more than the first 20layers, and still more preferably no more than the first 15 layers. Whenthis deep dipping variation is used, the depth of the deep dipping ispreferably at least about 2×, more preferably at least about 10×, morepreferably at least about 40×, still more preferably at least about 50×,and yet more preferably at least about 100× the desired layer thicknessΔz. At the same time, the depth of the deep dipping is preferably nomore than about 400×, still more preferably no more than about 350×,even more preferably no more than about 300×, and even more preferablyno more than about 200× the desired layer thickness Δz. Thus, in oneexample using a desired layer thickness Δz of 50 microns, the deepdipping depth ranges from 5-10 mm, which is 100-200 times the layerthickness. In preferred examples, when deep dipping is used,solidification of the next object layer is deferred until the levelingwait time expires starting from the time when the solidificationsubstrate assembly 57 is in the level configuration and the buildplatform 46 has been elevated so that the exposed object surface 82 isspaced apart from the solidification substrate assembly 57 by a distancealong the build (z) axis equal to the desired layer thickness Δz.

In accordance with the deep dipping variation, there is preferably awaiting period between the completion of the deep dipping step and theelevation of the build platform 46 to a build (z) axis location at whichthe exposed object surface 82 is spaced apart from the exposedsolidifiable material surface 51 by the desired layer thickness Δz. Inpreferred examples, the waiting period is preferably at least about one(1) second, more preferably at least about 1.5 seconds, and still morepreferably at least about 2 seconds. At the same time, the waitingperiod is preferably no more than about 10 seconds, still morepreferably no more than about 8 seconds, and even more preferably nomore than about 5 seconds. The deep dipping variation can be performedwith or without tilting the solidification substrate assembly 57 orperforming the leveling operation described above. However, if tiltingis not used to perform an object peeling operation, the speed of descentof the build platform 46 in the negative build (z) axis direction mustbe reduced because object separation from the film 60 will occur duringthe descent and without tilting, the separation forces per unit areawill generally be higher across the exposed object surface 82.

As indicated previously, the apparatus 40 of FIGS. 1A-1E preferablyincludes at least one controller that is operatively connected to theactuator 66. The at least one controller may comprise multiplecontrollers that are respectively used to control the actuator 66, thebuild platform motor (not shown), a linear solidification device motor(not shown) and internal components of the linear solidification device62, such as a source of solidification energy and a linear scanningdevice. Alternatively, these functions may be provided in a singlecontroller that includes the requisite inputs and outputs. A schematicillustration of a controller 184 that controls the linear solidificationdevice 62, tilting actuator 66, and build platform 46 is shown in FIG.3. Controller 184 includes a microprocessor 188 such as a centralprocessing unit (CPU). Controller 184 also includes a non-transitorymemory 186 that stores one or more programs (i.e., sets of computerexecutable instructions) which when executed by the processor 188 causethe controller 184 to perform various calculations and determinationsand to generate various output signals from outputs 194 to connecteddevices.

Controller 184 includes a variety of inputs 192 for receiving sensor orother instrument signals used to carry out control functions. In theexample of FIG. 3, controller 184 is connected to a pressure (or force)sensor 110, a build platform position indicator 208 (which may comprisea signal from a build platform motor that is indicative of the buildplatform 46 position along the build (z) axis), an actuator limit switch210, and a solidification energy sensor 211. Solidification energysensors are described in Applicant's co-pending U.S. patent applicationSer. No. 13/534,638, including in FIGS. 5C and 5D and corresponding textincluding at paragraphs 102-110, 191-196, and 209-212, the contents ofwhich are hereby incorporated by reference.

Controller 184 also includes a variety of outputs 194 for transmittingvarious actuation signals to different devices. In the example of FIG.3, controller outputs 194 are connected (either directly or indirectlyby way of intervening devices) to tilting actuator 66, build platformmotor 200, linear solidification device motor 201, solidification energysource 204, and linear scanning device 207. Controller 184 also includesdata ports 190 for receiving data from other devices. For example,controller 184 receives object data 198 that is representative of thethree-dimensional object and which dictates the pattern ofsolidification energy projected through the rigid or semi-rigidsolidification substrate 58 and film 60 and onto the exposed surface 51of the solidifiable material 50. In certain examples, a computer (notshown) processes object data received in a first format and transmits itin a second format to data ports 190. For example, a host computer mayreceive CAD/CAM data or other object data and convert it into stringdata comprising a plurality of time values at which a solidificationenergy source is toggled on and off as linear solidification device 62moves along the x-axis. Examples of string data are provided inApplicant's co-pending U.S. patent application Ser. No. 13/534,638,including in FIGS. 16(d), 16(f), and 16(g) and the corresponding text atparagraphs 167-170, and 176-181, the contents of which are herebyincorporated by reference.

Controller 184 is also operatively connected to a tilting parameterdatabase 196. The tilting parameter database 196 comprises anon-transitory, computer readable medium having tilting parameter datastored on it. The tilting parameter database 196 may be provided asinternal component in controller 184 or it may be a separate componentfrom which controller 184 receives necessary tilting parameter data. Inpreferred examples, the tilting parameter database 196 includes names orother identifiers for a plurality of different solidifiable materialsand a set of tilting parameters stored in association with eachsolidifiable material identifier. The set of tilting parameters for anygiven solidifiable material may comprise one or more tilting parameters.The tilting parameters may be selected from the group consisting ofactuator peeling distance Δa, peeling velocity, leveling velocity,leveling wait time, pressure (or force) sensor reference pressure,pressure (or force) sensor reference change with respect to time(dP/dt), and minimum object peeling travel distance Δg, and any and allcombinations thereof. In one exemplary implementation, controller 184includes a program comprising a set of computer executable instructionsstored in memory 186 and when executed by processor 188, the computerexecutable instructions determine an actuator peeling distance Δa from aminimum object peeling travel distance Δg (FIG. 1C) and an x-axislocation on the exposed object surface 82 that is closest to hinges 74 aand 74 b (i.e., the tilting axis) along the x-axis. The computerexecutable instructions then cause the controller 184 to generate anappropriate output signal (actuator activation signal) which istransmitted to the actuator 66 and which causes the actuator 66 toextend the distal shaft end 70 from the fully retracted position ofFIGS. 1A and 1B to the desired actuator peeling distance Δa. In afurther example, the computer executable instructions cause controller184 to generate an appropriate actuator activation signal to retract theactuator distal shaft end 70 to the fully retracted position of FIG. 1E.Further examples of suitable computer executable instructions aredescribed below with respect to FIGS. 7 and 8A-8B.

Referring to FIGS. 4A-4E, a detailed perspective view of an apparatusfor making a three-dimensional object is described. The apparatusincludes a solidification substrate assembly 57 and a work table 64. Theapparatus also comprises a housing 42, build platform 46 (and shaft 52)and solidifiable material container 44 which are not shown for ease ofillustration.

The solidification substrate assembly 57 includes a rigid or semi-rigidsolidification substrate 58, a rigid or semi-rigid solidificationsubstrate frame 88, load frame 120, film assembly 90, and linearsolidification device 62. The work table 64 includes a central openingin which the solidification substrate assembly 57 is disposed. Thesolidification substrate assembly 57 is tiltable about a tilting axisthat is defined by hinges 74 a and 74 b (FIG. 4D) and which is parallelto the y-axis. Hinges 74 a and 74 b are attached to the load frame 120and the work table 64 as shown in FIG. 4D. A stop 118 comprising asubstantially flat member extending along the y-axis is provided torestrain the tilting of the solidification substrate assembly 57 in adirection toward the build platform (not shown). A wire conduit 106 isprovided to connect at least one controller 184 to the linearsolidification device 62.

An exemplary solidification substrate assembly 57 (without the linearsolidification device 62 attached) is depicted in FIGS. 5A-5C. Rigid orsemi-rigid solidification substrate 58 is attached to a solidificationsubstrate frame 88 and projects beneath (along the build (z) axis) thesidewalls 132 a (not shown) and 132 b. Frame 88 is generally rigidstructure which is preferably metal. Solidification substrate frame 88includes first and second sidewalls 132 a and 132 b which are spacedapart along the y-axis, and cross-members 94 c and 94 d spaced apartalong the x-axis. The solidification substrate 58 has a bottom surfacethat projects beneath (along the z-axis) the lower surfaces of sidewalls132 a and 132 b. The solidification substrate 58 is positioned inward ofcross-members 94 c and 94 d along the x-axis and is attached tosidewalls 132 a and 132 b, which are spaced apart from one another alongthe y-axis.

Film assembly 90 includes a transparent and/or translucent film 60 and aframe assembly. The frame assembly comprises an inner frame 92 and anouter frame 91. The inner frame 92 includes an outwardly projecting lip138. A peripheral portion of the film 60 is sandwiched between the lip138 and the upper surface of the outer frame 91. The film 60 ispreferably stretched tautly within the frames 92 and 91. In certainexamples, film 60 may have a plurality of small grooves in its upwardfacing surface. In certain examples, the grooves minimize the likelihoodof a vacuum forming between downward (build (z) axis) surface of therigid or semi-rigid solidification substrate 58 and the upward (build(z) axis) facing surface of the film 60. However, such grooves are notnecessary in many implementations.

Load frame 120 is a generally rectangular structure with side walls 104a and 104 b spaced apart along the y-axis, and side walls 95 c and 95 dspaced apart along the x-axis. Actuator 66 includes actuator housing 67and shaft 68. As best seen in FIGS. 4B-4C, shaft 68 has a distal end 70.Actuator housing 67 has a proximal end 73. Thus, the distance from theproximal housing end 73 to the shaft distal end 70 along an axis definedby the length of shaft 68 defines the length of the actuator 66. Theactuator length is adjustable from a retracted configuration to anextended configuration. In the extended configuration, the distal end 70of shaft 68 is spaced apart along the shaft 68 length axis and along thebuild (z) axis from the actuator housing proximal end 73 by a distancethat is greater than the shaft 68 length axis and build (z) axisspacings between the distal end 70 and actuator proximal housing end 73in the retracted configuration. In the extended configuration, thedistal shaft end 70 is also spaced apart from a build platform (notshown) 46 by a distance along the build (z) axis that is greater thanwhen the actuator 66 is in the retracted configuration. The length axisof actuator shaft 68 is generally parallel to the build (z) axis and issubstantially parallel to the build (z) axis when the solidificationsubstrate assembly 57 is in a level configuration (FIG. 4A). However,the actuator shaft 68 length axis will tilt relative to the build (z)axis during a solidification substrate assembly tilt operation becausethe solidification substrate assembly 57 traverses a circular path whenviewed along the y-axis during a tilting operation. The actuator shaft68 will exhibit its maximum degree of tilt relative to the build (z)axis when the shaft distal end 70 reaches its fully extended position.

In the example of FIGS. 4A-4E, the position of the proximal end 73 ofactuator housing 67 is fixed relative to the work table 64, and theposition of the distal shaft end 70 relative to the work table 64 variesas the actuator 66 is adjusted from the retracted configuration to theextended configuration and vice-versa.

In FIG. 4A, the solidification substrate assembly 57 is in a level(untilted) configuration relative to work table 64. Actuator 66 is in aretracted configuration in which distal shaft end 70 is relativelycloser (along the build (z) axis) to work table 64 and a build platform46 (not shown) than when actuator 66 is in an extended configuration. InFIGS. 4B-4E, solidification substrate assembly 57 is in a tiltedconfiguration relative to work table 64. When solidification substrateassembly 57 is in the tilted configuration, actuator 66 is in anextended configuration in which the distal shaft end 70 is relativelyfarther (along the build (z) axis) from work table 64 and the buildplatform 46 (not shown) than when the actuator 66 is in a retractedconfiguration.

The apparatus for making three-dimensional objects of FIGS. 4A-4Eincludes the solidification substrate assembly 57 of FIGS. 5A-5C. Aswith the example of FIGS. 1A and 1E, and as shown in FIG. 4A, whenattached to work table 64, the film 60 and rigid or semi-rigidsolidification substrate 58 are spaced apart from the work table 64 inthe negative build (z) axis direction when the solidification substrateassembly 57 is in a level configuration. This arrangement allows thefilm 60 or substrate 58 (if film 60 is not provided) to be placed incontact with the exposed surface of the solidifiable material withoutsubjecting the work table 64 or the load frame 120 to contact with thesolidifiable material. Although not shown in FIGS. 4A-4E, film 60includes an object contacting surface 61 that faces the closed bottom 45of solidifiable material container 44 as illustrated in FIGS. 1A-1E. Inaddition, the build platform 46 of FIGS. 1A-1E would be provided, andthe object build surface 48 would face the object contacting surface 61of the film 60, the open top 47 of solidifiable material container 44and the linear solidification device 62.

The solidification substrate frame 88 and the film assembly 90 areattachable to one another to define an assembled unit. Fasteners 130a-130 d (FIGS. 5A-5B) are provided around the periphery of the outwardlyextending lip 138 of the inner frame 92 and engage correspondingthreaded holes 134 a-134 d in the bottom surfaces of the corners of thesolidification substrate frame 88. In addition, the load frame 120 isattachable to the solidification substrate frame 88. Solidificationsubstrate frame 88 includes knobs 96 a-96 b and 97 a-97 b. Knobs 96 a-96b include threaded shafts 139 a (not shown) and 139 b (FIG. 5B) whichengage threaded holes 137 a (not shown) and 137 b formed in the topsurface of side 95 c of load frame 120. Knobs 97 a-97 b include threadedshafts 133 a (not shown) and 133 b which engage corresponding holes 135a and 135 b formed in the top surface of side 95 d of load frame 120.

When solidification substrate frame 88 is attached to film assembly 90and to load frame 120 as described above, the three components define anassembled solidification substrate assembly 57 as shown in FIG. 5C (thelinear solidification device 62 is not shown in FIGS. 5A-5C). In theassembled condition of FIG. 5C, the film assembly frames 92 and 91 andfilm 60 are disposed beneath (along the z-axis) the load frame 120. Thesolidification substrate 58 is disposed beneath (along the z-axis) theload frame 120 and the outwardly extending lip 138 of the film assemblyinner frame 92. The downward (along the z-axis) facing surface ofsolidification substrate 58 abuttingly engages the upward (along thez-axis) facing surface of film 60. Knobs 96 a-96 d and 97 a-97 b can beloosened to separate and lift the solidification substrate frame 88 andfilm assembly 90 as a unit from load frame 120, which is useful formaintenance operations such as replacing film 60 and/or thesolidification substrate 58, if necessary.

Referring again to FIGS. 4A-4E, the depicted apparatus includes a linearsolidification device motor 98 which is operable to traverse the linearsolidification device 62 along the travel (x) axis. Linearsolidification device 62 slidably engages linear slides 108 a and 108 b(not shown) which extend along the x-axis and are spaced apart from oneanother along the y-axis. The linear solidification device 62 isconnected to linear bearings (not shown) that are spaced apart from oneanother along the y-axis, each of which engages a respective one of thelinear slides 108 a and 108 b (not shown). Linear solidification devicemotor 98 is connected to a rotating shaft 100 with a length along they-axis. Pulleys 102 a and 102 b (not shown) are spaced apart from themotor shaft 100 along the x-axis and from one another along the y-axis.The Respective timing belts 101 a and 101 b (not shown) are spaced apartfrom one another along the y-axis and engage the motor shaft 100 on oneend and one of the two pulleys 102 a and 102 b on the other end. Thepulleys 102 a and 102 b and timing belts are located in housings 115 aand 115 b, respectively.

The linear solidification device 62 is connected to each timing belt 101a and 101 b. Thus, operation of motor 98 causes the shaft 100 to rotateabout its longitudinal axis, which in turn causes the timing belts 101 aand 101 b to circulate. The circulation of the timing belts 101 a and101 b traverses the linear solidification device 62 along the x-axiswith its attached linear bearings slidably engaging the linear slides108 a and 108 b (not shown). Suitable configurations of a linearsolidification device motor, pulleys, timing belts, and linear slidesare provided in FIGS. 3-4 and 7-8 of Applicant's co-pending U.S. patentapplication Ser. No. 13/534,638 and the corresponding text at paragraphs84-85 and 124-125, the contents of which are hereby incorporated byreference.

As mentioned previously, load frame 120 includes first and second sidewalls 104 a and 104 b which are spaced apart along the y-axis. Loadframe 120 also includes third and fourth side walls 95 c and 95 d whichare spaced apart along the x-axis. Hinges 74 a and 74 b are attached toside 95 d of the load frame 120, as shown in FIG. 4D. Load frame 120also includes a latch 114 (not shown in FIGS. 5A-5C) that is used toreleasably secure the load frame 120 to the distal end 70 of the tiltingactuator shaft 68. Latch 114 includes a knob 116 attached to a slidinglatch shaft 122. A user can grip the knob 116 and slide it within y-axisgroove 126 to slide the latch shaft 122 along the y-axis direction. Afirst end of the shaft 122 can be selectively inserted into andretracted from an opening 124 in the distal end 70 of the tiltingactuator shaft 68. The engagement of the latch shaft 122 and theactuator shaft distal end opening 124 connects the load frame 120 to theactuator shaft 68. Once the latch shaft 122 is engaged in the opening124, a user can rotate the knob 116 in the x-z plane within verticalgroove 128. Vertical groove 128 is dimensioned to substantially preventthe latch shaft 122 from moving along the y-axis. Thus, the rotation ofthe knob 116 locks the load frame 120 and the actuator shaft 68 intoengagement with one another, thereby operatively connecting the actuator66 to the solidification substrate assembly 57 so that movement of theactuator shaft 68 causes the solidification substrate assembly 57 totilt about the tilting axis defined by hinges 74 a and 74 b. As bestseen in FIG. 4C, the engagement between the latch shaft 122 and theopening 124 in the distal end 70 of the actuator shaft 68 allows thedistal shaft end 70 to rotate relative to the latch 114 as thesolidification substrate assembly 57 is tilted. The rotation allows forrotation of the solidification substrate assembly 57 about hinges 74 aand 74 b such that the distal end 70 of the actuator shaft 68 willtraverse a circular path (when viewed along the y-axis) during tiltingoperations.

As discussed previously with respect to the example of FIGS. 1A-1E, incertain implementations a pressure (or force) sensor may be provided andused to determine when a squeezing operation is complete (i.e., todetermine when the squeezing of solidifiable material between an exposedobject surface and the film 60/substrate 58 is complete). In FIGS. 4A,4B, and 4E, a pressure sensor 110 in the form of a load cell is attachedto work table 64 on work table side 65 b. A load bracket 112 is disposedon the load frame 120 and engages the load cell 110 when thesolidification substrate assembly 57 is in a level configuration (FIG.4A) and disengages from the load cell 110 when the solidificationsubstrate assembly 57 is in a tilted configuration. An adjustment screw113 is provided, and its length of extension from load bracket 112 canbe adjusted to engage the load bracket 112 and the load cell 110. Thelength of extension of screw 113 from load bracket 112 can be adjustedto calibrate the orientation of the solidification substrate assembly 57relative to the x-y plane when the solidification substrate assembly 57is in the level or “home” position. In preferred examples, the length ofextension of screw 113 from load bracket 112 is adjusted so that therigid or semi-rigid solidification substrate 58 and/or film 60 aresubstantially or completely parallel to the x-y plane when thesolidification substrate assembly is in the level (home) position.

Pressure (or force) sensor 110 is configured to operate in the samemanner described previously with respect to pressure (or force) sensor86 of FIG. 2. In examples wherein pressure (or force) sensor 110 isprovided, it is preferably connected to controller 184 so that thepressure (or force) sensor 110 signal can be used by computer executableinstructions executed by processor 188 to determine when a levelingoperation is complete and an object solidification operation for a newlayer of solidifiable material can begin.

The actuator 66 depicted in FIGS. 4A-4E is an electromechanical linearactuator that includes a motor 69 connected to shaft 68. Controller 184is preferably connected to motor 69 or to a source of current suppliedto motor 69 to operatively connect the controller 184 and the actuator66. In certain examples, during peeling and/or leveling operations, thecontroller 184 generates an actuator activation signal having a valuethat corresponds to a desired tilting parameter. For example, in oneimplementation, the controller 184 is connected to a source of variablecurrent which is used to energize motor 69, and the current can bemodulated to obtain a desired peeling and/or leveling velocity. As withthe example of FIGS. 1A-1E, one or more limit switches may be providedto generate a signal when the actuator shaft distal end 70 has reached afully extended and/or fully retracted position. The limit switchsignal(s) may then be used by the computer executable instructionsresident in the controller memory 186 to carry out subsequentoperations. In one example, the computer executable instructions causecontroller 184 to begin transmitting a build platform activation signalto a build platform motor (not shown) to move the build platform 46 downby one layer thickness Δz along the build (z) axis once the limit switchgenerates a signal indicating that the actuator shaft 68 is fullyextended (or at some specified time after the limit switch generates thesignal). In another example or at the same time, the computer executableinstructions cause the controller 184 to generate an actuator activationsignal that tilts the rigid or semi-rigid solidification substrate 58and film 60 about the tilting axis and toward the build platform 46 whenthe limit switch generates a signal indicating that the actuator shaft68 is fully extended (or at some specified time after the limit switchgenerates the signal). In certain exemplary implementations, theactuator 66 applies a constant force against the solidificationsubstrate assembly 57 during an object peeling operation. In otherexemplary implementations, the actuator 66 applies a constant forceagainst the solidification substrate assembly 57 during a levelingoperation. In further exemplary implementations, the actuator 66 appliesa constant force against the solidification substrate assembly 57 duringboth an object peeling operation and a leveling operation (albeit inopposite directions). In a preferred method, the same constant force isapplied to the solidification substrate assembly 57 during an objectpeeling and a leveling operation (in opposite directions) and theconstant force (in the negative build (z) axis direction) used in theleveling operation remains after the solidification substrate assembly57 is level, which stabilizes the assembly 57 against the upwardpressure of the solidifiable material. In one example, a constant forceof 80 psi is applied to the solidification substrate assembly 57 duringboth an object peeling and a leveling operation.

In general, during leveling operations it is preferable to use aleveling wait time that ensures the squeezing of solidifiable materialbetween the exposed object surface 82 and the solidification substrateassembly 57 is substantially or entirely complete before beginning asolidification operation. However, in some cases, when thesolidification substrate assembly 57 is in the level configuration (FIG.1E) and solidification of the next layer of solidifiable material hasnot yet begun, it may be desirable to operate the actuator 66 to apply aforce that opposes the force of the solidifiable material 50 against thesolidification substrate assembly. This force may be referred to as the“level configuration force”. Applying a level configuration force to thesolidification substrate assembly 57 better ensures that if there areany fluid disturbances or other hydrodynamic phenomena, they do not movethe solidification substrate assembly 57. In the case of actuator 66 inFIGS. 1A-1E and 4A-4E, the opposing actuator force is applied in thedownward build (z) axis direction to oppose the force applied by thesolidifiable material 50 in the upward build (z) axis direction (seeFIG. 2). For actuator 66, the opposing force is applied by applying adownward build (z) axis force to actuator shaft 68 because it isconnected to the load frame 56 of solidification substrate assembly 57.

When actuator 66 is an electromechanical actuator, repeatedly applyingan opposing level configuration force to the solidification substrateassembly 57 can shorten the life of the motor 69 used to operate theactuator 66. Thus, in certain examples, the motor 69 is operated in amodified mode when the solidification substrate assembly 57 is in alevel configuration and solidification of the next layer of solidifiablematerial 50 has not yet begun. In one example, during at least a portionof the time in which the solidification substrate assembly 57 is in alevel configuration and solidification of the next object layer has notyet begun, the motor 69 is operated at less than 100 percent of the loadapplied during a leveling operation so that the level configurationforce is correspondingly reduced relative to the force applied as thesolidification substrate assembly 57 is being tilted during a levelingoperation (the “leveling operation force”) prior to reaching a levelconfiguration. In certain examples, the level configuration force is nomore than about 90 percent, preferably no more than about 80 percent,and still more preferably no more than about 70 percent of the levelingoperation force, and the motor 69 electrical load is correspondingly nomore than about 90 percent, preferably no more than about 80 percent,and still more preferably no more than about 70 percent of theelectrical load during a leveling operation. When a solidificationoperation begins by traversing the linear solidification device alongthe travel (x) axis and supplying solidification energy to thesolidifiable material along the scanning (y) axis, the electrical loadapplied to motor 69 is restored to 100 percent of the load appliedduring a leveling operation and remains there until solidification ofthe current layer is complete.

In another example, when the solidification substrate assembly 57 is ina level configuration and a solidification operation has not yet begun,the motor 69 electrical load is pulsed with alternating pulses ofdifferent magnitudes. In one implementation, the alternating pulsesinclude 100 percent of the load used during a leveling operation and avalue less than that load, which is preferably not more than about 70percent, more preferably not more than about 60 percent, and still morepreferably not more than about 50 percent of the load used during aleveling operation. When a solidification operation begins by traversingthe linear solidification device along the travel (x) axis and supplyingsolidification energy to the solidifiable material along the scanning(y) axis, the electrical load applied to motor 69 is restored to 100percent of the load applied during a leveling operation and remainsthere until solidification of the current layer is complete.

Referring to FIGS. 14A and 14B, examples of methods of operating themotor 69 to apply a leveling operation force and a level configurationforce are depicted. In each of the figures the letter “A” refers to aleveling operation during which the solidification substrate assembly 57is tilted toward the level configuration. In FIGS. 1A-1E, the actuator66 retracts from an extended position to a retracted position during theleveling operation, and thus applies a downward force along the build(z) axis to the solidification substrate assembly 57. The letter “B”refers to a level solidification substrate assembly 57 configuration inwhich a level configuration force is applied by the actuator 66 to thesolidification substrate assembly 57 but during which solidification ofthe solidifiable material 50 is not taking place. The letter “C” refersto a level solidification substrate assembly 57 configuration duringwhich solidification has begun. Thus, in phase C the linearsolidification device 62 travels along the travel (x) axis whileselectively supplying solidification energy along the scanning (y) axisin a pattern that corresponds to a portion of the three-dimensionalobject being built.

In FIG. 14A, during phase B the motor 69 electrical load drops to avalue that is less than 100 percent of the electrical load during phasesA and C. However, the load remains substantially constant or constantduring the entirety of phase B. In FIG. 14B, during phase B the motor 69electrical load is pulsed in alternating pulses of 100% and 50% of theloads during phases A and C. In the methods illustrated by FIGS. 14A and14B, during phase B there is at least some period of time during whichthe motor 69 load and the level configuration force are less than themotor 69 load and the force during a leveling operation (phase A) and asolidification operation (phase C). The motor 69 load and force duringphase B may be constant, variable, pulsed, or irregular. However, atsome point during phase B the motor 69 load and actuator 66 force areless than during phases A and C.

Referring to FIG. 6, another exemplary solidification substrate assembly57 and work table 64 apparatus for forming a three-dimensional objectfrom a solidifiable material is depicted. The apparatus is similar tothat of FIGS. 4A-4E in several respects and like numerals refer to likeparts. However, in the apparatus of FIG. 6 the actuator is a pneumaticactuator 166 that is attached in the opposite vertical (build axis)orientation of actuator 66. Pneumatic actuator 166 comprises a hydraulicfluid cylinder 169 and a shaft 168. Cylinder 169 includes a proximal end173 of the pneumatic actuator 166, and shaft 168 includes a distal end170 which is the distal end of the actuator 166. Thus, actuator 166 hasa length defined by a distance along the shaft 168 length axis betweenthe cylinder proximal end 173 and the shaft distal end 170. The lengthaxis of actuator shaft 168 is generally parallel to the build (z) axisand is substantially parallel to the build (z) axis when thesolidification substrate assembly 57 is in a level configuration shownin FIG. 6. However, the actuator shaft 168 length axis will tilt duringa solidification substrate assembly tilt operation because thesolidification substrate assembly 57 traverses a circular path whenviewed along the y-axis during a tilting operation. The actuator shaft168 will exhibit its maximum degree of tilt relative to the build (z)axis when the shaft distal end 170 reaches its fully retracted position.The actuator length is adjustable from a retractable configuration to anextended configuration and vice-versa. When the actuator 166 is in theextended configuration, the actuator distal end 170 is spaced apart(along the shaft 168 length axis and the build (z) axis) from thecylinder proximal end 173 by a distance that is greater than thedistance by which the actuator distal end 170 is spaced apart (along theshaft 168 length axis and the build (z) axis) from the cylinder proximalend 173 when the actuator 166 is in the retracted configuration. Whenactuator 166 is in the extended configuration, the actual distal end 170is spaced apart along the build (z) axis from the build platform (notshown in FIG. 6, but shown in FIGS. 1A-1E) by a distance that is shorterthan when the actuator 166 is in the retracted configuration.

The shaft 168 is partially and selectively retractable into andextendable from the interior of hydraulic fluid cylinder 169. Distal end170 of shaft 168 is connected to an upper surface of load frame 120 viabracket 172. Proximal end 173 of the cylinder 169 is attached to astationary mounting platform 140 via bracket 174. The stationarymounting platform 140 is connected to a housing (not shown). Theconnection between the distal end 170 of the shaft and the bracket 172allows the distal end 170 to rotate in the x-z plane relative to thebracket 172 to facilitate tilting about the tilting axis defined by thehinges 74 a and 74 b (not visible in FIG. 6). As a result, distal shaftend 170 will traverse a circular path when viewed along the y-axisduring solidification substrate assembly 57 tilting operations.

The position of the proximal end 173 of actuator 166 remains fixed withrespect to stationary mounting platform 140. However, the distal end 170of actuator shaft 168 is movable relative to the stationary mountingplatform 140 and relative to build platform 46 (not shown). Thus,extending the actuator 166 from the retracted configuration to theextended configuration causes the solidification substrate assembly 57(including the solidification substrate frame 88, solidificationsubstrate 58, film assembly 90, and linear solidification device 62) totilt about the tilting axis defined by hinges 74 a and 74 b (not visiblein FIG. 6) in a direction toward the build platform (not shown but wouldbe positioned underneath the film assembly 90 along the build (z) axis)and away from stationary mounting platform 140 until load frame bracket112 a reaches abutting engagement with load cell 110. Solidifiablematerial located between the film 60 of film assembly 90 and the buildplatform (not shown) would exert an upward force (and pressure) alongthe build (z) axis that will diminish as solidifiable material issqueezed out of the space between the exposed object surface 82 (FIGS.1A-1E) and object contacting surface 61 of film 60. As explained below,the signal generated by pressure (or force) sensor 110 can be used bycontroller 184 to determine when to supply solidification energy fromthe linear solidification device 62 to the solidifiable material. In oneexample, the pressure (or force) sensor 110 provides a pressure signalto the controller 184 via inputs 192 and once the pressure signalreaches a predetermined value (or within a fixed or variable timethereafter), solidification may begin. In another example, thecontroller 184 may determine the rate of change of the pressure signal(dP/dt), and solidification may begin once the rate of change of thepressure signal reaches a predetermined value (or within a fixed orvariable time thereafter).

Hydraulic fluid cylinder 169 comprises an interior volume of hydraulicfluid that engages a piston (not shown) on one end of shaft 168 that iscontained in the interior of the cylinder 169. As hydraulic fluid issupplied to the cylinder 169, the piston is displaced along the lengthof the cylinder 169 in the negative build (z) axis direction, causingthe distal end 170 of the shaft 168 to extend in the negative build (z)axis direction. Conversely, as hydraulic fluid is withdrawn fromcylinder 169, the piston moves in the positive build (z) axis direction,causing the distal end 170 of the shaft 168 to retract in the positivebuild (z) axis direction. Thus, in the apparatus of FIG. 6, when thedistal end 170 of the actuator shaft 168 is in its fully extendedposition along the build (z) axis, the solidification substrate assembly57 is in a level configuration, with the rigid or semi-rigidsolidification substrate 58 and film 60 substantially parallel to theupward facing surface 48 of the build platform 46 (FIGS. 1A-1E). Duringan object peeling operation, hydraulic fluid is withdrawn from thecylinder 169, causing the distal end 170 of the actuator shaft 168 toretract from an extended position to a retracted position. A verticalstop 171 comprising an annular ring is tightly engaged with the shaft168 and limits the retraction of the shaft 168 within the interior ofhydraulic fluid cylinder 169. The engagement of the piston (not shown)with the distal interior wall (not shown) of the cylinder 169 limits theextension of the shaft 168. A source of hydraulic fluid is also providedbut is not shown in FIG. 6. Controller 184 (FIG. 3) is operativelyconnected to the source of hydraulic fluid to selectively supply andwithdraw hydraulic fluid from the cylinder 169. In certain examples,controller 184 is operatively connected to a hydraulic fluid pump andgenerates an actuator activation signal having a value that correspondsto the flow rate of hydraulic fluid into the cylinder, which in turncorresponds to the speed of movement of the actuator shaft 168. When theshaft 168 is retracting into the cylinder 169, the speed of movement ofthe actuator shaft 168 is the peeling velocity. When the shaft 168 isextending from the cylinder 169, the speed of movement of the actuatorshaft 168 is the leveling velocity.

In certain exemplary implementations, the actuator 166 applies aconstant force against the solidification substrate assembly 57 duringan object peeling operation. In other exemplary implementations, theactuator 166 applies a constant force against the solidificationsubstrate assembly 57 during a leveling operation. In further exemplaryimplementations, the actuator 166 applies a constant force against thesolidification substrate assembly 57 during both an object peelingoperation and a leveling operation (albeit in opposite directions). In apreferred method, the same constant force is applied during an objectpeeling and a leveling operation, and the constant force (in thenegative build (z) axis direction) applied during the leveling operationremains after the solidification substrate assembly 57 is level (thelevel configuration force), which stabilizes the assembly against theupward pressure of the solidifiable material 50.

In the illustrated example of FIG. 6, the level configuration force isapplied by extending the actuator 166 from a retracted configuration toan extended configuration, which applies a downward build (z) axis forceto solidification substrate assembly 57 to oppose the upward build (z)axis force of the solidifiable material (FIG. 2). For actuator 166 theopposing downward build (z) force is applied by applying a downwardbuild (z) axis force to actuator shaft 168 because it is connected tothe load frame 56 of the solidification substrate assembly 57.

Actuator 166 is hydraulic but could also be motor-driven. If amotor-driven actuator 166 were used, level configuration forces may beapplied as described previously with respect to the apparatuses of FIGS.1A-1E and 4A-4E and as further illustrated in FIGS. 14A-B.

In the apparatus of FIG. 6, a second hydraulic actuator 176 is provided.The second hydraulic actuator 176 is used to tilt the entiresolidification substrate assembly 57 out of the central opening in thework table 64 and into a substantially upright condition. The secondhydraulic actuator 176 is not used for peeling or leveling operations. Aproximal end of the second hydraulic actuator 176 is connected to asecond stationary mounting platform 142 via bracket 182. A distal end ofthe second hydraulic actuator shaft 178 is connected to the load frame120 via bracket 180.

Referring to FIG. 7, a first method of making a three-dimensional objectusing a tilting solidification substrate assembly will now be described.Apparatuses useful for carrying out the method include, but are notlimited, to the apparatuses of FIGS. 1A-6, 10-13, and 16A-16F.

The steps described in FIG. 7 may be embodied as a set of computerexecutable instructions stored in memory 186 of controller 184. In step1010, object data which is representative of the three-dimensionalobject is read. The object data may be provided for the entire object atonce or just for one or more layers of the object. A layer index k isinitialized in step 1012 and incremented by one in step 1014. Based onthe object data for the current layer, a determination is made as to thefarthest x-axis coordinate for the layer in step 1016. The term“farthest” indicates that the location is the farthest from the actuator66, 166 and closest to the hinges 74 a and 74 b in a direction along thex-axis. The coordinate x_(max) will correspond to the last x-axisposition of the linear solidification device 62 at which solidificationwill occur for a given layer. For example, in the apparatuses of FIGS.1-6, the linear solidification device 62 will travel in two directionsalong the x-axis. However, object solidification operations will only becarried out while the linear solidification device 62 travels in one ofthe x-axis two directions. When viewing the apparatus of FIGS. 1A-1Ealong the y-axis and in the depicted orientation, solidificationoperations are carried out when the linear solidification device 62travels away from actuator 66 and towards the tilting axis defined bythe hinges 74 a and 74 b. The linear solidification device 62 alsotravels back in the opposite direction along the x-axis, but no objectsolidification operations are carried out. Similarly, in the apparatusesof FIGS. 4A-6, object solidification operations are performed when thelinear solidification device 62 travels along the x-axis in a directionaway from the actuator 66, 166 and toward the hinges 74 a and 74 b.However, solidification operations are not carried out when the linearsolidification device 62 moves along the x-axis in a direction towardthe actuator 66, 166 and away from the hinges 74 a and 74 b. Inapparatuses that use spatial light modulation techniques such as digitallight projectors, all locations on the exposed solidifiable materialsurface 51 which are to be solidified will be solidified simultaneously.Thus, x_(max) in FIGS. 1A-6 will be the x-axis location closest to thehinges 74 a and 74 b and farthest from the actuator 66, 166 but becausea spatial light modulation technique is used, there will be no movingsolidification energy source having a position along the x-axis thatdefines x_(max). If a two-dimensional laser drawing technique is used,the galvanometer mirrors will move in a pattern that defines theexposure pattern on the solidifiable material. For each layer, thepattern will have a value of x_(max).

In step 1018 the exposed surface 51 (FIGS. 1A-1E) of the solidifiablematerial 50 is exposed to solidification energy. In the case of aspatial light modulated system, the exposed surface 51 will receive oneor more two-dimensional energy patterns projected in the x-y plane asstatic images. In the case of a linear solidification device 62, thedevice 62 will travel along the x-axis and supply linear patterns ofsolidification energy with lengths along the y-axis in step 1018. Theexpression P(x,y) in step 1018 refers to the set of all x, y coordinatesat which solidification occurs. Since those x, y values will vary withthe layer, step 1018 indicates that P(x, y) is a function of the layer,i.e., P(k).

In step 1020 a determination is made as to whether each y-axis locationat the farthest x-axis location x_(max) has been solidified. In the caseof spatial light modulated systems, this step will be unnecessarybecause each y-axis location at a given x-axis location willsimultaneously receive solidification energy from the solidificationenergy source. However, in the case of linear solidification devices 62that use linear scanning devices, solidification energy will beprogressively supplied along the y-axis at a given x-axis location.Thus, the layer solidification will not be complete until each y-axislocation where solidification will occur at the farthest x-axis locationx_(max) has been solidified. If all such y-axis locations have not beensolidified, control returns to step 1018 and solidification along they-axis continues. Otherwise, solidification of the layer is complete andcontrol transfers to step 1022.

Referring to FIG. 3, if controller 184 is provided, in step 1018 thecontroller 184 will provide a signal to operate the linearsolidification device motor 98 to move linear solidification device 62along the x-axis. As the linear solidification device 62 moves along thex-axis, the controller 184 will also provide appropriate signals to thesolidification energy source 204 (e.g., a laser diode, such as laserdiode 90 shown and described in FIGS. 3, 4, and 5A-5D of Applicant'sco-pending U.S. patent application Ser. No. 13/534,638, filed on Jun.27, 2012 and the corresponding text, including at paragraphs 60-79 and86-104) and a linear scanning device (e.g., motor that rotates apolygonal mirror, such as motor 118 which rotates polygonal mirror 92 inU.S. patent application Ser. No. 13/534,638) to carry out a layersolidification operation. Even with linear solidification device 62,step 1020 will not be necessary if peeling is deferred until the linearsolidification device 62 completes its traversal of the entire buildenvelope (the x-y area of the resin that is subject to solidification)in the x-axis direction. However, step 1020 beneficially makes use ofthe dynamic assessment of object layer data to initiate peelingoperations as soon as possible, which further reduces overall objectbuild times.

In step 1022 at least one controller (e.g., controller 184 of FIG. 3)generates a first actuator activation signal to carry out a peelingoperation by tilting the solidification substrate assembly 57 away fromthe build platform 46. In the case of actuator 66, the first actuatoractivation signal will cause the shaft 68 to extend from a fullyretracted configuration to a fully extended configuration (unlessvariable actuator peeling distances are used, in which case the actuatorshaft 68 would not necessarily extend to a fully extended position). Inthe case of actuator 166, the first actuator activation signal willcause the shaft 168 to retract from a fully extended configuration to aretracted configuration. In certain preferred implementations, step 1022begins about one (1) second after the completion of a layersolidification operation in step 1018. In certain exemplaryimplementations, step 1022 is carried out using a peeling velocity of atleast about 0.1, preferably at least about 0.2, and more preferably atleast about 0.3 mm/seconds. At the same time, the peeling velocity is nomore than about one (1) mm/second, more preferably no more than about0.8 mm/second and still more preferably no more than about 0.7mm/second. In one exemplary implementation, a peeling velocity of 0.5mm/seconds is used. As mentioned previously, the peeling velocity refersto the linear speed of travel of the distal end 70, 170 of the actuatorshaft 68, 168 during a peeling operation.

A determination is made in step 1024 as to whether peeling is complete.If it is, control transfers to step 1026. Otherwise, control returns tostep 1024 and peeling continues. In certain implementations, a constantactuator peeling distance Δa is used and a limit switch is provided todetermine when the actuator shaft 68, 168 has reached the actuatorpeeling distance Δa. In other implementations, however, a variableactuator peeling distance Δg (FIG. 1C) may be calculated from objectdata and a desired minimum object peeling travel distance. In suchcases, other techniques may be used to determine whether the calculatedactuator peeling distance has been reached. In the case of hydraulicactuators, the total amount of hydraulic fluid that is supplied to orwithdrawn from the cylinder 169 may be used indicate the distance oftravel of the distal shaft end 70, 170. In the case of electromechanicalactuators, motor parameters such as activation time or both activationtime and current may be used to indicate the distance of travel ofdistal shaft end 70, 170.

In step 1026 the method determines if the final layer has beensolidified, as indicated by the value of the current layer index krelative to the index of the last object layer k_(max). If the lastlayer has been reached, the method ends. Otherwise, control transfers tostep 1028 to begin the process of providing a new layer of solidifiablematerial.

In step 1028 the build platform 46 (FIGS. 1A-1E) is moved downward inthe negative build (z) axis direction by one layer thickness Δz. Incertain exemplary implementations herein, the layer thickness Δz ispreferably no more than about 250 microns, still more preferably no morethan about 200 microns, more preferably no more than about 150 microns,even more preferably no more than about 100 microns, and yet morepreferably no more than about 60 microns. At the same time, the layerthickness Δz is preferably no less than about 10 microns, still morepreferably no less than about 20 microns, even more preferably no lessthan about 30 microns, and yet more preferably no more than about 40microns. In one example, a layer thickness Δz of about 50 microns isused. Step 1028 may be carried out during all or part of steps1022-1026. However, in preferred examples, step 1028 is carried outafter step 1024 indicates that peeling is complete. In many knownprocesses, the build platform 46 must be moved downward by greater thanthe desired layer thickness to separate the exposed object surface 82from the film 60. However, the method of FIG. 7 avoids the need formanipulating the build platform 46 to effect peeling. In the knownprocesses, the position of the build platform 46 when solidifying thelast object layer is necessarily limited by the requirement to drop theplatform 46 by an amount greater than the desired layer thickness. As aresult, solidifiable material is trapped in the container 44 at a heightequal to the distance beneath the layer thickness which the platform 46must be dropped to effect object separation from the film 60. Thistrapped solidifiable material cannot be used to form the object 78.Among other advantages, the method of FIG. 7 eliminates this trappingand maximizes the amount of solidifiable material available for formingthree-dimensional object 78.

In certain implementations, controller 184 receives a signal from thebuild platform motor indicating when the platform 46 has stopped in itsdescent. In such implementations, the leveling operation of step 1030 iscarried out either when the signal is received or within a fixed timethereafter. In such embodiments, the fixed time is preferably selectedto ensure that the descent of the build platform for the next layersolidification operation is complete. In other implementations, theleveling operation is carried out within a fixed time after an objectpeeling operation is complete.

Following the completion of step 1028, a leveling operation iscommenced. In step 1030 the controller (e.g., controller 184) willgenerate a second actuator activation signal to tilt the solidificationsubstrate assembly toward the build platform until the actuator shaft68, 168 reaches its “home” or “level” position. In the case of actuator66, the controller's issuance of the second actuator activation signalwill cause the distal end 70 of actuator shaft 68 to retract from afully extended to a fully retracted position (unless variable actuatorpeeling distances Δa are used in which case the actuator shaft 68 wouldnot necessarily start from a fully extended position). As describedpreviously with respect to FIG. 1E, once the leveling object iscomplete, solidifiable material may continue to “squeeze out” of thespace between the exposed object surface 82 and the film 60/rigid orsemi-rigid solidification substrate 58. It is preferable to defer thebeginning of another layer solidification operation until the squeezingoperation is complete. In step 1032 a determination is made as towhether a pressure sensor is present for use in determining whensqueezing is complete. Suitable pressure sensors include sensors 86(FIGS. 1A-1E) and 110 (FIGS. 4A, 4B, 4E, and 6) described previously. Ifa pressure sensor is present, in step 1034 the method waits until thepressure (or rate of change of pressure, dP/dt) indicated by the sensor86, 110 reaches a desired set point (step 1036). As explainedpreviously, the set point may comprise a value selected based on thenature of the solidifiable material. Once the sensed pressure reachesthe set point in step 1036 (or once the change in pressure with respectto time dP/dt reaches a certain threshold), control transfers to step1014 to increment the layer index and begin solidifying another layer.

In certain exemplary implementations, step 1028 is carried out using aleveling velocity of at least about 0.1, preferably at least about 0.2,and more preferably at least about 0.3 mm/seconds. At the same time, theleveling velocity is no more than about one (1) mm/second, morepreferably no more than about 0.8 mm/second and still more preferably nomore than about 0.7 mm/second. In one exemplary implementation, aleveling velocity of 0.5 mm/seconds is used. As mentioned previously, inthe apparatuses of FIGS. 1A-1E, 4A-4E, 6, and 16A-16F) the levelingvelocity is the linear speed of travel of the distal end 70, 170 of theactuator shaft 68, 168 during a leveling (squeezing) operation. Incertain examples, multiple leveling velocities may be used. In oneimplementation, higher leveling velocities are used at the beginning ofleveling, and lower leveling velocities are used toward the end ofleveling. The higher velocities are used while the solidificationsubstrate frame 88, load frame 120, and film assembly 90 tilt toward thebuild platform 46 before appreciable material squeezing beings and lowervelocities are used after squeezing begins. The beginning of appreciablesqueezing may be determined using pressure sensor 110, when thesolidification substrate assembly 57 reaches a particular tilt anglerelative to work table 64, or after a particular initial leveling periodhas expired.

If no pressure sensor is present in step 1032 (see the apparatus of FIG.4E), the method waits until a leveling wait time expires (step 1034).Once the leveling wait time expires, control transfers to step 1014 toincrement the layer index k and begin the solidification of anotherlayer. The leveling wait time and the pressure sensor setpoint (or dP/dtsetpoint) may comprise tilting parameters stored in the tiltingparameter database 196 (FIG. 3). In certain implementations, thecontroller 184 receives data indicating the identity of a solidifiablematerial selected by a user and uses the identified solidifiablematerial to query the tilting parameter database 196 and retrieve a setof tilting parameters corresponding to the identified solidifiablematerial. Illustrative examples of database records in the tiltingparameter database 196 will be described further below with reference toFIG. 9. Leveling wait times of no more than about five (5), preferablyno more than about three (3), and still more preferably not more thanabout two (2) seconds are preferred. At the same time, leveling waittimes of at least about 0.25, preferably at least about 0.5, and morepreferably at least about 0.8 seconds are preferred. In oneimplementation, a leveling wait time of about one (1) second is used.

In certain implementations of the method of FIG. 7, it has been foundthat during the first several layers of an object solidificationoperation, it may not be possible to obtain sufficient solidifiablematerial above the exposed object surface to develop a new layer ofsolidifiable material of the desired layer thickness. In suchimplementations, the deep dipping process described with respect toFIGS. 1A-1E is preferably implemented for the first several layers ofthe object. Thus, in accordance with this variation, step 1028 ismodified during the formation of the first several layers of the objectsuch that the build platform is dipped in the negative build (z) axisdirection by an amount greater than the desired layer thickness Δz andis subsequently elevated in the positive build (z) axis direction untilthe exposed object surface 82 is spaced apart from the exposedsolidifiable material surface by the desired layer thickness Δz. Inpreferred implementations of this variation, the deep dipping step iscarried out during the formation of at least layer 2, more preferablyduring layers 2-3, still more preferably during layers 2-4, even morepreferably during layers 2-5, still more preferably during layers 2-6,yet more preferably during layers 2-7, even more preferably duringlayers 2-8, and still more preferably during layers 2-9, and yet morepreferably during layers 2-10. The deep dipping process is preferablycarried out for no more than the first 30 layers, even more preferablyno more than the first 20 layers, and still more preferably no more thanthe first 15 layers. When this deep dipping variation is used, the depthof the deep dipping is preferably at least about 2×, more preferably atleast about 10×, more preferably at least about 40×, still morepreferably at least about 50×, and yet more preferably at least about100× the desired layer thickness Δz. At the same time, the depth of thedeep dipping is preferably no more than about 400×, still morepreferably no more than about 350×, even more preferably no more thanabout 300×, and even more preferably no more than about 200× the desiredlayer thickness Δz. Thus, in one example using a desired layer thicknessΔz of 50 microns, the deep dipping depth ranges from 5-10 mm, which is100-200 times the layer thickness. In preferred examples, when deepdipping is used, solidification of the next object layer is deferred(step 1034) until the leveling wait time expires after thesolidification substrate assembly 57 is in the level configuration andthe build platform 46 has been elevated so that the exposed objectsurface 82 is spaced apart from the solidification substrate assembly 57by a distance along the build (z) axis equal to the desired layerthickness Δz.

In accordance with the deep dipping variation, there is preferably awaiting period between the completion of the deep dipping step and theelevation of the build platform 46 to a build (z) axis location at whichthe exposed object surface 82 (FIGS. 1B-1E) is spaced apart from theexposed solidifiable material surface 51 (FIG. 1D) by the desired layerthickness Δz. In preferred examples, the waiting period is preferably atleast about one (1) second, more preferably at least about 1.5 seconds,and still more preferably at least about 2 seconds. At the same time,the waiting period is preferably no more than about 10 seconds, stillmore preferably no more than about 8 seconds, and even more preferablyno more than about 5 seconds. The deep dipping variation can beperformed with or without tilting the solidification substrate assemblyor performing the leveling operation described above. However, iftilting is not used to perform an object peeling operation, the speed ofdescent of the build platform 46 in the negative build (z) axisdirection must be reduced because object separation from the film 60will occur during the descent and without tilting, the separation forcesper unit area will generally be higher across the exposed objectsurface.

Referring to FIGS. 8A-8B, a second method of making a three-dimensionalobject using a tilting solidification substrate assembly 57 will now bedescribed. Apparatuses useful for carrying out the method include butare not limited to the apparatuses of FIGS. 1A-6 and 10-13. As with themethod of FIG. 7, the method of FIGS. 8A-8B may be carried out by acomputer executable process steps stored in the non-transitory memory ofthe controller and executed by the controller's processor. Leveling waittimes of no more than about five (5), preferably no more than aboutthree (3), and still more preferably not more than about two (2) secondsare preferred. At the same time, leveling wait times of at least about0.25, preferably at least about 0.5, and more preferably at least about0.8 seconds are preferred. In one implementation, a leveling wait timeof about one (1) second is used.

In step 1040, object data representative of the three-dimensional objectis read. In step 1042 a user's selection of a solidifiable materialidentifier is read (e.g., “Envisiontec E-Denstone”). The materialidentifier is used as a database query key to retrieve a set of tiltingparameters comprising one or more tilting parameters from a tiltingparameter database such as the tilting parameter database 196 of FIG. 3.In step 1044, the set of tilting parameters corresponding to theselected solidified material is retrieved. The set of tilting parametersincludes one or more of the following, alone or in combination: anactuator peeling distance Δa, a minimum object peeling travel distanceΔg, a reference peeling velocity, a reference leveling velocity, apeeling velocity, a leveling velocity, a leveling wait time, and aleveling pressure sensor set point. In addition to or in lieu of theleveling pressure set point, a rate of pressure change (dP/dt) thresholdmay be provided as a tilting parameter.

To begin an object building operation, a layer index k is nextinitialized (step 1046) and then incremented by one (1) (step 1048). Instep 1050, the object data is used to identify an x-axis location ofsolidification that is closest to the tilting axis (i.e., the hinges 74a and 74 b in FIGS. 1A-1E, 4A-4E and 6) and farthest from the actuator66, 166. The expression f(k) in step 1050 refers to the fact that thevalue of x_(max) depends on the particular layer, and therefore, thevalue of the layer index k.

In the method of FIG. 8A, one or more tilting parameter values arecalculated based on object data representative of the object. Step 1052exemplifies such a technique. In this step, the value of the actuatorpeeling distance Δa is determined for the current layer by determiningthe peeling distance Δa that would cause the part of the film 60 incontact with the exposed object surface 82 at x_(max) to travel by alinear distance of Δg. In general, points on the film 60 in contact withthe exposed object surface 82 at x_(max) will travel in a circular pathduring peeling operations. The starting location and ending location ofthe points will define linear vectors between the starting and endinglocations, and the value of Δa is selected so that the lengths of theselinear vectors are equal to Δg. This technique tunes the amount ofpeeling to the particular x-axis profile of each object layer, therebyminimizing the amount of peeling and reducing peeling times. In certainexamples, equation (1) may be used to calculate Δa. In an alternativeimplementation of step 1052, the x-axis coordinate of the build platformlocation that is closest to the tilting axis and farthest from theactuator is used as x_(max). In this implementation, the actuatorpeeling distance Δa is not adjusted based on the object data but may beadjusted based on the solidifiable material by providing values of Δg ina tilting parameter database that vary depending on the material used.

Step 1054 provides another example of calculating a tilting parameterbased on object data. In step 1054 the area of the exposed objectsurface 82 is calculated from object data representative of thethree-dimensional object using known techniques. It is believed thatcertain tilting parameters are beneficially adjusted based on theexposed surface area of a three-dimensional object. In step 1056 amodified peeling velocity is calculated from a reference (or initial)peeling velocity in the tilting parameter database 196. In oneimplementation, the reference peeling velocity is based on a referenceexposed object surface area, and the modified peeling velocity iscalculated by dividing the determined value of the exposed objectsurface area 82 for the current layer by the reference surface area andmultiplying that ratio by the reference peeling velocity. A modifiedleveling velocity may also be calculated in this manner. However, ingeneral, it is believed that adjusting the peeling velocity based on theexposed object surface area is more beneficial than adjusting theleveling velocity based on it.

In step 1058 the portions of the exposed solidifiable material surfacethat are to be solidified (P(x,y)) are solidified. The set of P(x,y)will vary with the particular layer, and therefore, with the value ofthe layer index k. If each y-axis position at x_(max) has beensolidified, the layer solidification operation is complete and controltransfers to step 1062. Otherwise, control returns to step 1058 tocontinue solidification.

A peeling operation is commenced in step 1062. A controller such ascontroller 184 generates a first actuator activation signal having asignal value that corresponds to the modified peeling velocity. In oneexample, the first actuator activation signal is a variable current, thevalue of which causes the actuator 66 to extend the distal end 70 of theactuator shaft 68 at the modified peeling velocity. Using the apparatusof FIG. 6, hydraulic fluid is withdrawn from cylinder 169 at a rate thatcauses actuator 166 to retract the distal end 170 of actuator shaft 168at the modified peeling velocity.

In step 1062 the solidification substrate assembly 57 tilts away fromthe build platform 46 as shown in FIGS. 1C and 1D. Because the actuatorpeeling distance Δa is variable in the method of FIGS. 8A and 8B, instep 1064 a determination is made as to whether the actuator distal end70 has reached the modified actuator peeling distance Δa. If it has,control transfers to step 1066. Otherwise, step 1062 is continued untilthe modified actuator peeling distance Δa is reached. In certainpreferred implementations, step 1062 begins no more than about one (1)second after the completion of a layer solidification operation in step1058.

In certain exemplary implementations, step 1062 is carried out using apeeling velocity of at least about 0.1, preferably at least about 0.2,and more preferably at least about 0.3 mm/seconds. At the same time, thepeeling velocity is no more than about one (1) mm/second, morepreferably no more than about 0.8 mm/second and still more preferably nomore than about 0.7 mm/second. In one exemplary implementation, apeeling velocity of 0.5 mm/seconds is used.

In step 1066 the layer index k is compared to the maximum layer indexfor the entire object k_(max). If the maximum index k_(max) has beenreached, the object is complete and the method ends. Otherwise, controltransfers to step 1070 to begin the process of forming a new layer ofsolidifiable material. In step 1070 the build platform 46 (FIGS. 1A-1E)is moved away from the rigid or semi-rigid solidification substrate 58and the film 60 by one layer thickness Δz. As illustrated in FIG. 3,this step may be carried out by having controller 184 issue a signal tothe build platform motor to cause it to operate and move the buildplatform downward by the desired amount. In certain variations of themethod of FIGS. 8A and 8B, steps 1070 and 1062 are carried outconcurrently. In preferred implementations, the time between thecompletion of peeling as determined in step 1064 and the commencement ofleveling in step 1072 is no more than one (1) second.

The controller then generates a second actuator signal having a signalvalue that corresponds to the leveling velocity (or modified levelingvelocity if one is calculated from the object data for the layer) (step1072). Step 1072 causes the solidification substrate assembly 57 to tiltabout the tilting axis toward the build platform 46 until reaching the“home” or “level” position. In certain implementations, controller 184receives a signal from the build platform motor (not shown) indicatingwhen the platform 46 has stopped in its descent. The leveling operationof step 1030 is carried out either when the signal is received or withina fixed time thereafter. Alternatively, leveling may begin after theexpiration of a fixed time from the beginning of the build platformmovement or after the expiration of a fixed time after the completion ofpeeling if the time is selected to ensure that build platform movementis complete before leveling begins. In certain exemplaryimplementations, step 1072 is carried out using a leveling velocity ofat least about 0.1, preferably at least about 0.2, and more preferablyat least about 0.3 mm/seconds. At the same time, the leveling velocityis no more than about one (1) mm/second, more preferably no more thanabout 0.8 mm/second and still more preferably no more than about 0.7mm/second. In one exemplary implementation, a leveling velocity of 0.5mm/seconds is used.

In step 1074 a determination is made as to whether a leveling pressuresensor such as sensors 86 and 110 is present. If one is present, controltransfers to step 1078. In step 1078 the method compares the currentpressure (or force) sensor reading to the setpoint to determine if thesqueezing of solidifiable material is complete. Once the pressurereaches a reference set point, squeezing is considered to be completeand control transfers to step 1048 to begin another layer solidificationoperation. In another implementation, step 1074 may be carried out bydetermining the rate of change of the pressure (dP/dt) or force (dF/dt)and comparing it to a threshold value that indicates when squeezing ofsolidifiable material is complete.

If step 1074 indicates that no leveling pressure sensor is present,control transfers to step 1076. In step 1076 the next layersolidification operation is deferred until the expiration of theleveling wait time. Once the leveling wait time expires, controltransfers to step 1048 to begin another layer solidification operation.Leveling wait times of no more than about five (5), preferably no morethan about three (3), and still more preferably not more than about two(2) seconds are preferred. At the same time, leveling wait times of atleast about 0.25, preferably at least about 0.5, and more preferably atleast about 0.8 seconds are preferred. In one implementation, a levelingwait time of about one (1) second is used.

In certain implementations of the method of FIGS. 8A-8E, it has beenfound that during the first several layers of an object solidificationoperation, it may not be possible to obtain sufficient solidifiablematerial above the exposed object surface to develop a new layer ofsolidifiable material of the desired layer thickness. In suchimplementations, the deep dipping process described with respect toFIGS. 1A-1E is preferably implemented for the first several layers ofthe object. Thus, in accordance with this variation, step 1070 ismodified during the formation of the first several layers of the objectsuch that the build platform is dipped in the negative build (z) axisdirection by an amount greater than the desired layer thickness Δz andis subsequently elevated in the positive build (z) axis direction untilthe exposed object surface 82 is spaced apart from the exposedsolidifiable material surface by the desired layer thickness Δz. Inpreferred implementations of this variation, the deep dipping step iscarried out during the formation of at least layer 2, more preferablyduring layers 2-3, still more preferably during layers 2-4, even morepreferably during layers 2-5, still more preferably during layers 2-6,yet more preferably during layers 2-7, even more preferably duringlayers 2-8, and still more preferably during layers 2-9, and yet morepreferably during layers 2-10. The deep dipping process is preferablycarried out for no more than the first 30 layers, even more preferablyno more than the first 20 layers, and still more preferably no more thanthe first 15 layers. When this deep dipping variation is used, the depthof the deep dipping is preferably at least about 2×, more preferably atleast about 10×, more preferably at least about 40×, still morepreferably at least about 50×, and yet more preferably at least about100× the desired layer thickness Δz. At the same time, the depth of thedeep dipping is preferably no more than about 400×, still morepreferably no more than about 350×, even more preferably no more thanabout 300×, and even more preferably no more than about 200× the desiredlayer thickness Δz. Thus, in one example using a desired layer thicknessΔz of 50 microns, the deep dipping depth ranges from 5-10 mm, which is100-200 times the layer thickness. In preferred examples, when deepdipping is used, solidification of the next object layer is deferred(step 1076) until the leveling wait time expires after thesolidification substrate assembly 57 is in the level configuration andthe build platform 46 has been elevated so that the exposed objectsurface 82 is spaced apart from the solidification substrate assembly 57by a distance along the build (z) axis equal to the desired layerthickness Δz.

In accordance with the deep dipping variation, there is preferably awaiting period between the completion of the deep dipping step and theelevation of the build platform 46 to a build (z) axis location at whichthe exposed object surface 82 (FIG. 1D) is spaced apart from the exposedsolidifiable material surface 51 by the desired layer thickness Δz. Inpreferred examples, the waiting period is preferably at least about one(1) second, more preferably at least about 1.5 seconds, and still morepreferably at least about 2 seconds. At the same time, the waitingperiod is preferably no more than about 10 seconds, still morepreferably no more than about 8 seconds, and even more preferably nomore than about 5 seconds. The deep dipping variation can be performedwith or without tilting the solidification substrate assembly 57 orperforming the leveling operation described above. However, if tiltingis not used to perform an object peeling operation, the speed of descentof the build platform 46 in the negative build (z) axis direction mustbe reduced because object separation from the film 60 will occur duringthe descent and without tilting, the separation forces per unit areawill generally be higher across the exposed object surface.

As discussed previously, in certain implementations of the apparatusesand methods described herein, one or more tilting parameters areprovided in a tilting parameter database 196 (FIG. 3). The tiltingparameter database 196 preferably associates a set of tilting parameterscomprising at least one tilting parameter with one of several varioussolidifiable materials. A user may then select a material identifier ona computer user interface provided with the apparatus. Computerexecutable program instructions stored in the controller memory 186 thenuse the selected material to query the tilting parameter database 196.The query returns the set of tilting parameters associated with theselected material identifier which is then used to carry out tiltingoperations. FIG. 9 depicts three exemplary records of a tiltingparameter database 196. In the depicted example, three solidifiablematerial identifiers are provided 214 a-214 c. Each record associates aminimum object peeling travel distance 216 b (Δg), a peeling velocity216 c, a leveling velocity 216 d, a leveling wait time 216 e, and areference squeezing pressure 216 f with one of the solidifiable materialidentifiers 215 a-215 c. Thus, a user wishing to build an object withEnvisiontec E-Denstone would make a corresponding entry into a userinterface provided with the apparatus for making a three-dimensionalobject. The selected entry would be transmitted to the controller 184and used by the computer executable process instructions to perform adatabase query and retrieve the tilting parameter values in the firstrow of the table (FIG. 9). In certain variations of the tiltingparameter database 196, the peeling velocity is a reference peelingvelocity based on a particular exposed object surface area and is usedby the computer executable program instructions stored in the controllermemory 186 to calculate a modified peeling velocity based on adetermined exposed object surface area for the layer of interest. Inanother variation, a fixed actuator peeling distance Δa is used in lieuof one calculated from a minimum object peeling distance Δg.

The use of the tilting parameter database 196 allows tilting parametersto be adjusted based on the particular materials used to make asolidifiable object. This tuning of the tilting process to thesolidifiable material avoids the need for setting fixed tiltingparameters that should function for all potential solidifiable materialswhich can result in excessive object build times.

Referring to FIGS. 10-13, another exemplary solidification substrateassembly 57 and work table 64 are depicted for use in an apparatus formaking at three-dimensional object such as apparatus 40 of FIGS. 1A-1E.Like numerals in FIGS. 10-13 refer to like components in FIGS. 1A-1E,4A-4E, 5A-5C and 6. Unlike the other apparatuses, however, in theexample of FIGS. 10-13 two actuators 266 a and 266 b are providing fortilting the solidification substrate assembly 57 about a tilt axisdefined by hinges 74 a and 74 b (not shown in FIGS. 10-13, but shown inFIG. 4D on side 65 a of work table 64.

Actuators 266 a and 266 b are spaced apart along the y-axis. Actuator266 a includes a housing 267 a and a shaft 268 a (not visible in thefigures). Actuator housing 267 a includes a proximal end 220 a, andshaft 268 a includes a distal end 270 a. A portion of shaft 268 a isdisposed in actuator housing 267 a and guide bushing 206 a. Guidebushing 206 a is fixedly attached to and stationary with respect toactuator housing 267 a. However, the spacing between the guide bushing206 a and the distal end 270 a of shaft 268 a is adjustable when theactuator 266 a is adjusted between an extended configuration and aretracted configuration (and vice-versa). Guide bushing 206 a isprovided to facilitate the adjustment of the actuator 266 a from aretracted configuration to an extended configuration and reduces theamount of vibration occurring during the adjustment process. In theretracted configuration, the actuator length defined by the distancebetween the actuator housing proximal end 220 a and the distal shaft end270 a is smaller than the distance between the actuator housing proximalend 220 a and distal shaft end 270 a when actuator 266 a is in theextended configuration.

Similarly, actuator 266 b includes a housing 267 b and a shaft 268 b(visible in FIG. 13). Actuator housing 267 b includes a proximal end 220b, and shaft 268 b includes a distal end 270 b. A portion of shaft 268 bis disposed in actuator housing 267 b and guide bushing 206 b. Guidebushing 206 b is fixedly attached to and stationary with respect toactuator housing 267 b. However, the spacing between guide bushing 206 band the distal end 270 b of shaft 268 b is adjustable when the actuator266 b is adjusted between an extended configuration and a retractedconfiguration (and vice-versa). Guide bushing 206 b is provided tofacilitate the adjustment of the actuator 266 b from a retractedconfiguration to an extended configuration (and vice-versa) and reducesthe amount of vibration occurring during the adjustment process. In theretracted configuration, the actuator length defined by the distancebetween the actuator housing proximal end 220 b and the distal shaft end270 b is smaller than the distance between the actuator housing proximalend 220 b and distal shaft end 270 b when actuator 266 b is in theextended configuration. In the extended configuration, the distancealong the build (z) axis from the actuator proximal ends 220 a, 220 b tothe build platform (not shown in FIGS. 10-13, but shown in FIGS. 1A-1E)is greater than in the retracted configuration.

In FIG. 10 the solidification substrate assembly 57 is shown in a levelconfiguration as would be the case following a leveling operation. Thelinear solidification device 62 may solidify solidifiable materialunderneath film assembly 90 as it moves in either or both directionsalong the x-axis. In FIG. 11 the solidification substrate assembly 57 isshown in an open configuration that is not used during the manufactureof a three-dimensional object.

Unlike the examples of FIGS. 1A-1E, 4A-4E, and 6, in the example ofFIGS. 10-13, the actuator distal ends 270 a and 270 b remain fixed withrespect to work table 64 while making a three-dimensional object from asolidifiable material. However, the actuator housings 267 a and 267 band their respective proximal ends 220 a and 220 b are movable along thebuild (z) axis relative to work table 64. Thus, in the example of FIGS.10-13, the actuator peeling distance Δa, for each actuator is equal tothe distance of travel of each actuator proximal end 220 a and 220 balong the length axis of its respective shaft 268 a and 268 b during anobject peeling operation. The length axes of actuator shafts 268 a and268 b are generally parallel to the build (z) axis and are substantiallyparallel to the build (z) axis when the solidification substrateassembly 57 is in a level configuration (as shown in FIG. 10). However,the actuator shaft 268 a and 268 b length axes will tilt during asolidification substrate assembly 57 tilt operation because thesolidification substrate assembly 57 traverses a circular path whenviewed along the y-axis during a tilting operation. The actuator shafts268 a and 268 b will exhibit their maximum degree of tilt relative tothe build (z) axis when their respective actuator proximal housing ends273 a and 273 b reach their fully extended positions.

To provide the foregoing configuration, latches 214 a and 214 b aremounted on the work table 64. A detailed view of latch 214 b and itsrelated components is shown in FIG. 13. Latch 214 a is configured andoperates similarly with analogous components. Referring to FIG. 13,latch shaft 222 b is slidable in groove 226 b within latch 214 b toselectively attach distal shaft end 270 b to work table 64 or detachdistal shaft end 270 b from work table 64, as desired. Latch shaft 222 bpreferably has a knob such as knob 116 in FIGS. 4B and 4C, but the knobis not shown in FIG. 13. The distal end 270 b of actuator shaft 268 bincludes an opening that can selectively receive latch shaft 222 b toattach distal end 270 b to the latch 214 b, thereby attaching distalshaft end 270 b to the work table 64. In FIG. 13, latch 214 b is in alatched condition, with latch shaft 222 b extending through an openingin shaft distal actuator end 270 b and an opening in latch 214 b.Although not visible in the figures, latch 214 a is configured similarlyto allow distal shaft end 270 a to be selectively attached to ordetached from the work table 64. In FIG. 11, latches 214 a and 214 b areshown in an unlatched condition.

Actuators 266 a and 266 b may be energized by motors or by hydraulicpower. In either case, during an object peeling operation, the actuatorhousings 267 a and 267 b move upward along their respective shaft lengthaxes and along the build (z) axis relative to work table 64 and buildplatform 46 (FIGS. 1A-1E). During a leveling operation, the actuatorhousings 267 a and 267 b move downward along their respective shaftlength axes and the build (z) axis relative to work table 64 and buildplatform (FIGS. 1A-1E). The movement of the actuator housings 267 a and267 b along the build (z) axis causes the load frame 120 to tilt aboutthe tilt axis defined by hinges 74 a-74 b (not shown in FIGS. 10-13, butshown in FIG. 4D) which also causes the remainder of the solidificationsubstrate assembly 57 to tilt about the tilt axis.

As best seen in FIG. 13, actuator housing 267 b is connected to the loadframe 120 via vertical actuator support 205 b and horizontal support 203b. Bracket 221 b is connected to proximal actuator end 220 b at a pivotaxis 223 b which allows the actuator 266 b to pivot relative to bracket221 b, horizontal actuator supports 203 b, and vertical actuator support205 b. This pivoting action allows the actuators 266 a and 266 b to tiltsuch that their respective length axes tilt relative to the build (z)axis during solidification substrate assembly 57 tilting operations asthe solidification substrate assembly traverses a circular path whenviewed along the y-axis.

As actuator 266 b is adjusted from a retracted configuration to anextended configuration (during an object peeling operation), theactuator proximal end 220 b exerts an upward (build (z) axis) forceagainst bracket 221 b, which in turn exerts an upward force againsthorizontal actuator support 203 b. The horizontal actuator support 203 bexerts an upward (build (z)) axis force against the vertical actuatorsupport 205 b, which in turn exerts an upward (build(z)) axis forceagainst the side 95 d (FIGS. 12A and 12B) of load frame 120 to tilt theload frame 120 about the tilt axis defined by hinges 74 a-74 b (FIG.4D). Actuator housing 267 a is connected to load frame 120 in a similarmanner by a bracket 221 a and actuator supports 203 a and 205 a whichare not shown in FIG. 13.

In FIG. 10, the actuator proximal end brackets 221 a and 221 b areconfigured somewhat differently from those shown in FIG. 13. Inaddition, the actuators 266 a and 266 b in FIG. 10 do not haveindividual horizontal supports 203 a and 203 b connecting the actuators266 a and 266 b to vertical actuator supports 205 a and 205 b,respectively. Instead, a cross-beam 202 is provided and is attached tobrackets 221 a and 221 b, respectively, and to the actuator verticalsupports 205 a and 205 b, respectively. The guide bushings 206 a and 206b are fixedly attached to their respective actuators 266 a and 266 b.The guide bushing holder 218 is connected to the vertical actuatorsupports 205 a and 205 b. Thus, during an object peeling or levelingoperation, the guide bushing holder 218 and the guide bushings 206 a and206 b preferably move along the build (z) axis relative to the worktable 64, build platform 46 (FIGS. 1A-1E) and relative to the distalactuator ends 270 a and 270 b.

As best seen in FIGS. 12A and 12B, load frame brackets 212 a and 212 bare provided on side 95 d of load frame 120 and are sized to overlapwith work table side 65 b along the x-axis. The load frame brackets 212a and 212 b act as stops to restrain the downward build (z) axismovement of the solidification substrate assembly 57. In addition, loadframe bracket 212 b is positioned to engage pressure (or force) sensor110 attached to work table side 65 b. As with the examples of FIGS.4A-4E, and 6, the solidification substrate assembly 57 and work table 64of FIGS. 10-13 may be used in apparatus 40 of FIGS. 1A-1E, in which caseeach new layer of solidifiable material will be provided between anexposed object surface (such as surface 82 in FIGS. 1B-1D) and film 60of film assembly 90. The solidifiable material 50 in the space betweenthe exposed object surface 82 and film 60 will exert an upward force andpressure that will decrease the force or pressure sensed by the pressure(or force) sensor 110. The upward force exerted by the solidifiablematerial 50 will decrease as solidifiable material is squeezed out ofthe space between the exposed object surface 82 and the film 60 untilreaching an equilibrium value.

As shown in FIGS. 12A and 12B, bracket 212 a includes a screw 213 a withan adjustable length along the build (z) axis which allows the stopposition of the load frame 120 along the build (z) axis on a firsty-axis side of the load frame 120 to be selectively adjusted.Correspondingly, bracket 212 b includes a screw 213 b with an adjustablelength along the build (z) axis which allows the stop position of theload frame 120 on a second y-axis side of the load frame 120 to beselectively adjusted. In certain examples, the screws 213 a and 213 bare adjusted to ensure that the solidification substrate 58 defines aplane that is substantially or completely perpendicular to the build (z)axis and parallel to the x-y plane.

Controller 184 of FIG. 3 may be used with the solidification substrateassembly 57 and work table 64 of FIGS. 10-13 and may be configured withthe same inputs and outputs. However, outputs 194 are preferablyconfigured to provide outputs to both actuators 266 a and 266 b. In thecase of hydraulic actuators, separate hydraulic pumps and conduits maybe provided for each actuator 266 a and 266 b (in which case thehousings 267 a and 267 b would be hydraulic cylinders), and thecontroller outputs 194 may include separate outputs for each pump or acommon output provided to each pump. Alternatively, a single pump maysupply fluid to both actuators 266 a and 266 b. In the case ofmotor-driven actuators, separate motors may be provided for eachactuator 266 a and 266 b, and outputs 194 may include separate outputsfor each motor or a common output provided to each motor. In eithercase, the controller 184 and the source of motive power for actuators266 a and 266 b are preferably configured so that the actuator housings267 a and 267 b move along the build (z) axis at the same rate relativeto one another to avoid the exertion of uneven forces against load frame120 along the y-axis.

The two actuator design of FIGS. 10-13 is particularly useful for largerbuild envelope machines to ensure that the solidification substrateassembly 57 may be stably tilted about the tilting axis. It is alsosometimes useful to use two linear solidification devices positionedadjacent one another along the y-axis for larger build envelope machinesinstead of linear solidification device 62. An example of such a duallinear solidification device configuration is provided in FIG. 36 andparagraphs 0266-271 of U.S. patent application Ser. No. 13/774,355, theentirety of which is hereby incorporated by reference.

The methods of FIGS. 7, 8A and 8B may be readily adapted for use withthe apparatus of FIGS. 10-13. In certain examples, the actuatoractivation signals are provided to a source of motive power (e.g., anelectric motor or hydraulic fluid pump) used to adjust the length of theactuators 266 a and 266 b along the build (z) axis as the actuators 266a and 266 b are adjusted from a retracted to an extended configuration(and vice-versa). For example, the method of FIG. 7A may be carried outas described previously. However, step 1022 would be modified togenerate two first actuator activation signals for each of actuator 266a and 266 b (or by supplying the same signal to each actuator). Thedetermination of whether peeling is complete in step 1024 may be made byusing a limit switch associated with either or both actuators 266 a and266 b or based on the operation of the respective motors or hydraulicpumps. Step 1030 would be modified to generate two second actuatoractivation signals for each of actuator 266 a and 266 b or to generate asingle actuator activation signal provided to each actuator 266 a and266 b. Pressure (or force) sensor 110 may be used to carry out step1032, or alternatively, a leveling wait time may be used.

Referring to FIGS. 8A and 8B, in step 1052 the calculated actuatorpeeling distance Δa used may be used to determine the extent that therespective actuator housings 267 a and 267 b will move along the lengthaxes of their respective actuator shafts 268 a and 268 b relative totheir respective distal shaft ends 270 a and 270 b and the work tableside 65 b (as well as relative to a build platform such as the buildplatform 46 of FIGS. 1A-1E). In step 1062, respective actuatoractivation signals (or a common actuator activation signal) may beprovided to the sources of motive power (e.g., motors or hydraulicpumps) to adjust the rate at which the lengths of the actuators 266 aand 266 b change to correspond to the modified peeling velocitydetermined in step 1056. Step 1064 may be carried out by determiningwhether the change in the lengths of either or both actuators 266 a and266 b have reached the calculated peeling distance Δa. Step 1072 may becarried out by generating two actuator activation signals for therespective sources of motive power used to adjust the lengths ofactuators 266 a and 266 b from the extended configuration to theretracted configuration. Alternatively, a common actuator activationsignal may be supplied to the source of motive power for each actuator266 a and 266 b.

In certain exemplary implementations, the actuators 266 a and 266 bapply a constant force against the solidification substrate assembly 57(by virtue of their connection to vertical actuator supports 205 a and205 b) during an object peeling operation. In other exemplaryimplementations, the actuators 266 a and 266 b apply a constant forceagainst the solidification substrate assembly 57 during a levelingoperation. In further exemplary implementations, the actuators 266 a and266 b apply a constant force against the solidification substrateassembly 57 during both an object peeling operation and a levelingoperation (albeit in opposite directions). In a preferred method, thesame constant force is applied to the solidification substrate assembly57 during an object peeling and a leveling operation (in oppositedirections) and the constant force (in the negative build (z) axisdirection) used in the leveling operation remains after thesolidification substrate assembly 57 is level, which stabilizes theassembly 57 against the upward pressure of the solidifiable material. Inone example, a constant force of 80 psi is applied to the solidificationsubstrate assembly 57 during both an object peeling and a levelingoperation.

In certain preferred examples, when solidification substrate assembly 57is in a level configuration and solidification of the next layer ofsolidifiable material 50 has not yet begun, actuators 266 a and 266 bapply a level configuration force, as described previously with theexamples of FIGS. 1A-1E, 4A-4E, and 6 and as illustrated in FIGS. 14Aand 14B. In the case of actuators 266 a and 266 b, the levelconfiguration force is applied by applying a downward force in the build(z) axis direction against the brackets 221 a and 221 b, which in turnapplies an downward force in the build (z) axis direction against thevertical actuator supports 205 a and 205 b, each of which is connectedto the load frame 56.

In certain examples, the tiltable solidification substrate assemblies 57described herein and illustrated in FIGS. 1A-1E, 4A-4E, 6, 10-13, and16A-16F are particularly beneficial when the solidifiable material 50 isof a relatively higher viscosity than a relatively lower viscosity.Preferred solidifiable material 50 viscosities (at 25° C.) are atgreater than 1500 cp, more preferably at least about 1800 cp, still morepreferably at least about 2000 cP, even more preferably at least about2500 cp, and yet more preferably at least about 2800 cP. As explainedpreviously, during a leveling operation, solidifiable material 50 is“squeezed out” of the space between the most recently formed objectsurface 82 (FIG. 1E) and the solidification substrate assembly 57. Insome examples, it is preferable to wait until the flow and movement ofsolidifiable material 50 between the exposed object surface 82 and thesolidification substrate assembly 57 has substantially or completelystopped following a leveling operation. In some embodiments, thesolidification of a next layer of solidifiable material 50 is deferreduntil the expiration of a leveling wait time (FIG. 9) to better ensurethat the localized flow and movement of the solidifiable material 50between the exposed object surface 82 and the solidification substrateassembly 57 has substantially or completely stopped. Without wishing tobe bound by any theory, it is believed that the flow and movement ofhigher viscosity solidifiable materials tends to stabilize more rapidlythan that of lower viscosity materials following a leveling operation.In certain preferred examples, the flow and movement of higher viscositysolidifiable materials with viscosities in the range described abovebetween the exposed object surface 82 and the solidification substrateassembly substantially or completely stops at leveling wait times thatare no more than about 20 seconds, preferably no more than about 15seconds, and still more preferably no more than about 10 seconds.

In certain examples, controller 184 (FIG. 3) includes a program thatcomprises a set of computer executable steps stored in non-transitorymedium 186 that operates the tiltable solidification substrateassemblies 57 described herein in two different modes, depending on theviscosity of the solidifiable material 50. In one example, a viscositythreshold is selected and used to classify solidifiable material 50 hasa “low viscosity material” or a “high viscosity material.” When executedby processor 188, the computer executable steps receive data indicatingwhether the solidifiable material 50 is a low viscosity material or ahigh viscosity material. If the solidifiable material 50 is a lowviscosity material, the controller 184 operates in a “low viscositymode”, in which computer executable steps cause the actuator (66, 166,266) to apply a level locking force to the solidification substrateassembly 57 that locks the solidification substrate assembly 57 in alevel configuration. The level locking force may be constant orvariable. In certain examples, the level locking force is higher duringan object solidification operation (e.g., when linear solidificationdevice 62 is traveling along the travel (x) axis and projectingsolidification energy along the scanning (y) axis) than during all orpart of the period when an object solidification operation is notoccurring. In other examples, the level locking force follows one of thepatterns shown in phase B in FIGS. 14A and 14B when an objectsolidification operation is not occurring and follows the pattern shownin phase C during an object solidification operation.

In some examples of the low viscosity mode, “deep dipping” operationsmay be required to supply a sufficient amount of solidifiable materialbetween the most recently formed exposed object surface 82 and thesolidification substrate assembly 57. In certain cases in which theactuator 66, 166, 266 a/b is motor-driven, the level locking force ispreferably higher during all or part of the time during which the buildplatform 46 is moved upward along the build (z) axis toward thesolidification substrate assembly 57 than after the build platform 46has reached a position at which the most recently formed exposed objectsurface 82 is spaced apart from the solidification substrate assembly 57by the desired layer thickness Δz.

In certain low viscosity operation examples wherein the actuators 66,166, 266 a/b are motor-driven, the actuator motor electrical loads mayfollow the load patterns depicted in FIGS. 14A and 14B. In such cases,phase “A” represents the period during which the build platform 46 ismoving upward along the build (z) axis toward the solidificationsubstrate assembly 57, phase “B” represents the period during which (1)no solidification is occurring and (2) the build platform 46 has stoppedmoving and is positioned so that the exposed object surface 82 (FIG. 1E)is spaced apart from the solidification substrate assembly 57 by thedesired layer thickness Δz, and phase “C” represents the period duringwhich an object solidification operation is occurring and the buildplatform 46 remains spaced apart from the solidification substrateassembly by the desired layer thickness Δz.

In accordance with the foregoing, when controller 184 receives dataindicating that the solidifiable material 50 is a “high viscositymaterial,” the processor 188 will execute a set of computer executablesteps stored in non-transitory memory 186 which will cause the actuators66, 166, and 266 a/b to carry out object peeling and leveling operationsas described previously herein. The controller 184 may also apply alevel configuration force to solidification substrate assembly 57 whenthe substrate 58 is level and no object solidification is occurring suchthat the level configuration force differs from the force applied duringa leveling operation and during an object solidification operation. Incertain examples, controller 184 executes the computer executableprocess steps applicable to a low viscosity material when the controller184 receives data indicating that the viscosity of the solidifiablematerial (at 25° C.) is no more than 1500 cp, more preferably less thanabout 1200 cp, and still more preferably less than about 1000 cp. Thecontroller 184 may receive actual viscosity data or may instead may beprogrammed to select the low viscosity mode of operation or the highviscosity mode of operation based on a material identifier of the typeshown in FIG. 9. In certain examples, the “low viscosity mode” ofoperation is used for those materials that still experience appreciableflow and movement more than about 20 seconds, more preferably more thanabout 15 seconds, and still more preferably more than about 10 secondsafter a leveling operation is complete. Otherwise, the “high viscosity”mode of operation is used.

Referring to FIG. 15, a dual-mode method of making a three-dimensionalobject from a solidifiable material using an apparatus with a tiltablesolidification substrate assembly is depicted. The method of FIG. 15includes two modes of operation, one for “high viscosity” solidifiablematerials and one for “low viscosity” solidifiable materials. The methodmay be used, for example, with any of the tiltable solidificationsubstrate assemblies 57 shown in FIGS. 1A-1E, 4A-4E, 10-13, and 16A-16F.In certain examples, “high viscosity” materials are those thatsubstantially stabilize so that no localized flow occurs between theexposed object surface 82 and the solidification substrate assembly 57within a specified leveling wait time after the solidification substrateassembly 57 assumes a level configuration. In certain examples, thespecified leveling wait time is no more than about 20 seconds,preferably no more than about 15 seconds, and still more preferably notmore than about 10 seconds.

In the same or other examples, “high viscosity” materials are those witha viscosity at 25° C. that is greater than 1500 cp, more preferably atleast about 1800 cp, still more preferably at least about 2000 cP, evenmore preferably at least about 2500 cp, and yet more preferably at leastabout 2800 cP. In step 1082 a determination is made as to whether thesolidifiable material 50 is high viscosity. In certain examples,controller 184 (FIG. 3) is provided and receives data indicative of theviscosity of the solidifiable material 50. The data may be viscositydata. It may also be a solidifiable material identifier such as thoseshown in field 216 a of FIG. 9, which is then identified as a high orlow viscosity material via another database accessed by controller 184.

In step 1082 if the solidifiable material 50 is a high viscositymaterial, control transfers to step 1084 to initialize the layer indexk. In step 1084 the layer index k is incremented. In step 1088 a layerof thickness Δz (FIG. 1E) is solidified. In examples where a linearsolidification device 62 is provided, the solidification of a layer iscarried out by traversing the linear solidification device 62 along thetravel (x) axis while supplying solidification energy along the scanning(y) axis. For SLM based methods, one or more two-dimensionalsolidification energy patterns will be projected as an image onto theexposed surface 51 of the solidifiable material to carry out step 1088.

In step 1090 an object peeling operation is carried out by tilting thesolidification substrate assembly 57 about the tilting axis (e.g.,hinges 74 a and 74 b in FIGS. 1A-1E, 4A-4E, 6 and 10) in a directionaway from build platform 46. Step 1090 will separate the solidificationsubstrate assembly 57 from the exposed object surface 82. Thus, in step1092 the method determines if the last layer of the object has beensolidified by comparing the current value of the layer index k to themaximum value k_(max). If solidification is complete, the method ends.Otherwise, control transfer to step 1094.

In step 1094 build platform 46 is moved away from solidificationsubstrate assembly 57 in direction along the build (z) axis by an amountthat is at least equal to the next desired layer thickness Δz. Incertain cases, it may be desirable to use “deep dipping” for all or partof the object building process, in which case the build platform 46 willinitially move away from the solidification substrate assembly 57 byalong the build (z) axis by an amount that is greater than the nextdesired layer thickness Δz and then moved back toward the build (z) axisto a position where the exposed object surface is spaced apart from thelevel configuration position of the solidification substrate assembly 57by the desired layer thickness Δz. Step 1094 may be carried outconcurrently with step 1090, but is preferably carried out after step1090. In step 1096 a leveling operation is carried out by tilting thesolidification substrate assembly about the tilting axis toward thebuild platform 46.

In step 1098 the method waits for the expiration of a “leveling waittime” so that the flow of solidifiable material 50 between the exposedobject surface 82 and the solidification substrate assembly 57substantially or completely stops. Step 1098 preferably begins when thesolidification substrate assembly 57 is in the level configuration andthe exposed object surface 82 is spaced apart from the solidificationsubstrate assembly 57 by the desired layer thickness and ends after theleveling wait time has elapsed. Following step 1098, control transfersto step 1086 and the layer index k is incremented to begin thesolidification of the next layer. If a motor driven actuator (oractuators) is used, during step 1098, level configuration forces may beapplied as described previously with respect to the apparatuses of FIGS.1A-1E and 4A-4E and as further illustrated in FIGS. 14A-B.

If step 1082 returns a value of NO (“N”), the solidifiable material is a“low viscosity material” and control transfers to step 1100 toinitialize the layer index k. In step 1102 the layer index k isincremented. In step 1104 the current layer is solidified as describedpreviously for step 1088. In step 1106 the build platform 46 is movedaway from the solidification substrate assembly 57 in a direction alongthe build (z) axis as in step 1092. For low viscosity materials, sinceobject peeling operations are not used, the most recently formed exposedobject surface 82 is separated from the solidification substrateassembly 57 (e.g., from the film 60 or rigid/semi-rigid substrate 58)during step 1106. In general, the speed of descent of the build platform46 in the negative build (z) axis direction in step 1106 must be reducedrelative to step 1094 because object separation from the film 60 willoccur during the descent and without tilting, the separation forces perunit area will generally be higher across the exposed object surface.Step 1106 may be carried out using the deep dipping techniques describedpreviously for some or all of the object layers.

In step 1108 the method determines whether the last layer has beensolidified, in which case the layer index k will equal the maximum valuek_(max) of the layer index k. If the last layer has been reached, themethod ends. Otherwise, control transfers to step 1110.

Step 1110 begins when the build platform 46 is positioned so that theexposed object surface 82 is spaced apart from the solidificationsubstrate assembly 57 by a distance along the build (z) axis equal tothe layer thickness Δz. The step ends once the squeezing time(comparable to a leveling wait time when tilting is not used) expires.During all or part of step 1110, a level locking force may be applied tothe solidification substrate assembly 57 in step 1110 which is less thanthe level locking force used during step 1104, as described previouslywith respect to FIGS. 14A and 14B.

In certain examples of the apparatuses for manufacturingthree-dimensional objects described herein, the solidification substrateassembly 57 may include a solidification substrate laminate 298 insteadof a film assembly 90. Certain types of solidifiable materials 50 have adegree of brittleness (when solidified) which causes them to break whenseparating from film 60 of film assembly 90. This is particularly thecase for finely dimensioned structures such as removable object supportsused to connect the object 78 to build platform 46 (FIGS. 1A-1E). In theexample of FIGS. 1A-1E, 4A-4E, 6, and 10-13, film 60 is supported by aframe but is not bonded to the rigid or semi-rigid solidificationsubstrate 58. As a result, during an object peeling operation, the film60 will deform along the build (z) axis and then quickly and resilientlyseparate from the object 78 in an abrupt manner which can damage theobject 78, and in particular, finely dimensioned object structures.

Referring to FIGS. 16A-16F, a modified version of the apparatus formaking three-dimensional objects of FIGS. 4A-4E is depicted. Likenumerals in FIGS. 16A-16F and 4A-4E refer to like parts. The apparatusof FIGS. 16A-16F includes the actuator 66 and latch 114 configuration ofFIGS. 4A-4E, and the load frame 120 is hinged to the work table 64 inthe same manner. The apparatus of FIGS. 16A-16F would also be providedwith a solidifiable material container 44 and build platform 46 as shownin FIGS. 1A-1E as well as the controller 184 and associated inputs andoutputs shown in FIG. 3.

In FIGS. 16A-16F, the solidification substrate assembly 57 includes asolidification substrate laminate 298 but does not include the filmassembly 90 of FIGS. 4A-4E. The solidification substrate laminate 298includes a rigid or semi-rigid solidification substrate 58 that istransparent and/or translucent. However, one or more films or coatingsare adhered to the rigid or semi-rigid solidification substrate tocreate a layered or laminate structure. The solidification substratelaminate 298 is operatively connected to at least one actuator and istiltable within the open top 47 of solidifiable material container 44about a tilting axis defined by hinges 74 a and 74 b (FIG. 4D).

Exemplary illustrations of solidification substrate laminate 298 areprovided in FIGS. 17A-17C. Solidification substrate laminate 298 isdepicted in an exaggerated perspective view to better illustrate layers58, 300, and 302. A typical exemplary laminate 298 will be significantlythinner and flatter than shown in the figure. In each of the examples ofFIGS. 17A-17C, solidification substrate laminate 298 comprises rigid orsemi-rigid solidification substrate 58, which is described above. Eachsolidification substrate laminate 298 includes an object contactingsurface 301 that faces the closed bottom 45 of solidifiable materialcontainer 44. However, the materials comprising object contactingsurface 301 may vary as described below.

In certain examples, solidification substrate laminate 298 is providedwith a localized area of resiliency proximate the exposed surface 51(FIGS. 1C and 1D) of solidifiable material 501. Referring to FIGS. 17Aand 17C, a transparent and/or translucent resilient layer 300 isprovided. A variety of different translucent and/or transparentresilient materials may be used for layer 300. When provided as a 10 mmlayer, the resilient layer 300 preferably transmits at least about 60percent of received light in the 325-700 nm range. The resilient layer300 preferably has a 10 mm layer transmission percentage of at leastabout 70 percent, more preferably at least about 80 percent, and evenmore preferably at least about 88 percent for light in the 325-700 nmrange. The resilient layer 300 preferably also has a percent elongationat break (according to ISO 37) that is at least about 80 percent, morepreferably at least about 90 percent, even more preferably at leastabout 95 percent, and still more preferably at least about 100 percent.In addition, resilient layer 300 preferably has a tensile strength(according to DIN ISO 37) that is at least about 3.0 N/mm², morepreferably at least about 5.0 N/mm², even more preferably at least about6.0 N/mm², and still more preferably at least about 7.0 N/mm².

Resilient layer 300 may be formed from one or more elastomeric polymers.In one example, silicone elastomers are provided. One particular exampleof a suitable silicone elastomer is Elastosil® RT 601, which is suppliedby Wacker Silicones. Elastosil® RT 601 is a transparent, addition-curingsilicone rubber having greater than 88 percent transmission of light inthe 325-700 nm range (for a 10 mm layer). The material has an elongationat break of about 100 percent (ISO 37), and a tensile strength of about7.0 N/mm2 (DIN ISO 37) tear strength (ASTM D 624B) of about 3.0 N/mm².Resilient layer 300 may be connected to rigid or semi-rigidsolidification substrate 58 (FIG. 17A) using known techniques. In oneexample, an adhesive such as a pressure sensitive adhesive is used tobond resilient layer 300 and rigid or semi-rigid solidificationsubstrate 58 together. The adhesive preferably does not significantlyalter the wavelengths of intensities of electromagnetic radiationtransmitted through substrate 58.

Certain solidifiable materials 50 may include components that chemicallydegrade resilient layer 300. For example, when certain photoinitiatorsare used to cure polymeric resins, the solidification process may bedamage layer 300. Accordingly, in certain examples and as shown in FIG.17A, a translucent and/or transparent protective layer 302 is provided.Translucent protective film 302 is preferably a homopolymer or copolymerformed from ethylenically unsaturated, halogenated monomers.Fluoropolymers are preferred. Examples of suitable materials forprotective film 302 include polyvinylidene fluoride (PVDF),ethylenchlorotrifluoroethylene (ECTFE), ethylenetetrafluoroethylene(ETFE), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), andmodified fluoroalkoxy (a copolymer of tetrafluoroethylene andperfluoromethylvinylether, also known as MFA). Examples of suitableprotective film 302 materials include PVDF films sold under the Kynar®name by Arkema, ECTFE films sold under the Halar® name by SolvaySolexis,ETFE films sold under the Tefzel® name by DuPont, PFA films sold underthe Teflon®-PFA name by DuPont, and MFA films sold under the nameNowofol.

In one example, solidification material 50 (FIGS. 1A-1E) comprises a 1,6hexanediol diacrylate and/or trimthelolpropane triacrylate (TMPTA) withan acylphosphine oxide initiator, such as Irgacure 819. Without wishingto be bound by any theory, it is believed that thephotopolymerization/photocrosslinking reaction that occurs generates anamount of heat that can damage resilient layer 300. Accordingly, in suchexamples an MFA protective film layer 302 is provided to reduce theeffect of the generated heat on translucent resilient layer 300. Inanother example, solidification material 50 comprises 1,6 hexanedioldiacrylate and/or TMTPA with a Darocur TPO initiator. Again, it isbelieved that the photopolymerization/photocrosslinking reactiongenerates an amount of heat that may damage elastomeric translucentlayer 300. Accordingly, in such examples, an MFA protective film layer302 is provided. Protective layer 302 may be bonded to resilient layer300 with an adhesive, such as a pressure sensitive adhesive. Theadhesive preferably does not significantly alter the wavelengths ofintensities of electromagnetic radiation transmitted throughsolidification substrate laminate 298.

In certain cases, the force required to separate a solidified section ofobject 78 from solidification substrate laminate 298 will be low enoughthat the resiliency provided by resilient layer 300 will not berequired. However, protective film 302 may still be used to protect therigid or semi-rigid solidification substrate 58. Referring to FIG. 17B,a solidification substrate laminate 298 is provided which comprisesrigid or semi-rigid solidification substrate 58 and translucent and/ortransparent protective film 302. In certain examples a slipping agent isincluded in the composition of solidifiable material 50, allowing forbetter release of solidified object 80 from solidification substrate 58,eliminating the need for a resilient layer. Suitable slipping agentsinclude TEGORAD 2250 from the Degussa Company and silicone agent EFKA7454 from the EFKA Company. In certain other cases, thephotopolymerization/photocrosslinking reaction proceeds without damagingthe resilient translucent and/or transparent layer 300 or rigid orsemi-rigid solidification substrate 58 through the generation of excessheat or otherwise. In such cases, protective film 302 is not required.Referring to FIG. 17C, a solidification substrate laminate 298 isprovided which comprises a rigid or semi-rigid translucent and/ortransparent solidification substrate 58 and an elastomeric translucentand/or transparent layer 300. In one example, a resin such as TMPTA,IBOA, or Ebecryl 3500 is used with an Irgacure 784 initiator and noprotective film is required.

Referring again to FIGS. 16A-16F, solidification substrate laminateframe 388 is provided and releasably secures solidification substratelaminate 298 to the solidification substrate assembly 57. Thesolidification substrate laminate frame 388 is shown in greater detailin FIGS. 16C and 16D. Solidification substrate laminate frame 388 isgenerally rectangular and made from a rigid metal or plastic. Sidewalls391 a and 391 b are spaced apart along the y-axis, and sidewalls 389 aand 389 b are spaced apart along the x-axis. Cross members 94 c and 94 dare spaced apart along the x-axis and also include knobs 97 a-97 b and96 a-96 b for securing the solidification substrate laminate frame 388to the load frame 120 (FIGS. 16A-16B). Latches 392 a and 392 b areattached to solidification substrate laminate frame sidewalls 389 a and389 b, respectively, via respective openings 402 a (not shown) and 402 b(FIG. 16C). Each latch 392 a and 392 b is also connected to acorresponding clamp member 390 a and 390 b. The clamp members 390 a and390 b each have respective openings 403 a and 403 b which receive andsecure latch fastener members 400 a and 400 b. The latch fastener member400 a extends through solidification substrate laminate frame side wallopening 402 a (not shown) and into clamp member opening 403 a. Latchfastener member 400 b extends through solidification substrate laminateframe side wall opening 402 b and into clamp member opening 403 b.

As shown in FIG. 16C, each clamp member 390 a and 390 b has respectivehorizontal lip 394 a and 394 b and a respective vertical wall 396 a and396 b. The sidewalls 389 a and 389 b each have a respective lowersurfaces 395 a and 395 b (FIGS. 16C-16F). Each lip 394 a and 394 b andits corresponding side wall lower surface 395 a and 395 b defines anadjustable spacing Δh along the build axis for receiving thesolidification substrate laminate 298 (FIG. 16F). The latches 392 a and392 b have a securing position and a releasing position. When thelatches 392 a and 392 b are in a securing position, the adjustablespacing Δh is at a minimum to securely retain solidification substratelaminate 298 to solidification substrate laminate frame 388. When thelatches 392 a and 392 b are in a releasing position, the adjustablespacing Δh is at a maximum to allow the solidification substratelaminate 298 to be removed from or inserted into the solidificationsubstrate laminate frame 388. Solidification substrate laminate stops398 a and 398 b are connected to solidification substrate laminate framemember 391 a and are spaced apart from one another along the x-axis tolimit the y-axis movement of the solidification substrate laminate 298as it is inserted along the y-axis from the solidification substratelaminate frame side 391 b to the solidification substrate laminate frameside 391 a. FIG. 16A shows the solidification substrate laminate 298secured to solidification substrate laminate frame 388 (the laminate 298is not shown in FIGS. 16B and 16D). Latches 392 a and 392 b are in thesecured position, in which the latches are oriented parallel to theirrespective frame side members 389 a and 389 b. To release thesolidification substrate laminate 298 from the frame 388, the latches392 a and 392 b are lifted into an orientation in which they areperpendicular to their respective frame members 389 a and 389 b. Thus,the rigid or semi-rigid solidification substrate laminate 298 may beremoved from the solidification substrate laminate frame 388 while theframe 388 remains secured to the load frame 120. Thus, if necessary, thesolidification substrate laminate 298 may be readily replaced by liftinglatches 392 a and 392 b into the releasing configuration to increase thespacing Δh between the clamp lips 394 a and 394 b and their respectiveframe member bottom surfaces 395 a and 395 b.

In certain examples, and as shown in FIGS. 16E-16F, plungers 405 a-405 dare provided so that the upper surface of the rigid or semi-rigidsolidification substrate 58 does not adhere to the underside of thesolidification substrate laminate frame 388. A sealing member 400 mayalso be provided on the underside 397 of the frame 388 to preventsolidifiable material 50 from flowing between upper surface of the rigidor semi-rigid solidification substrate laminate 298 and the underside397 of frame 388 into the inner portion of frame 388 between thesidewalls 389 a, 389 b, 391 a, and 391 b.

The solidification substrate laminate 298 is not shown in FIGS. 16D and16E. As FIG. 16D indicates the solidification substrate laminate frame388 and the laminate 298 can be removed as an integral unit from thesolidification substrate assembly 57. However, in the example of FIGS.16A-16F, the laminate 298 can be removed from the assembly 57 withoutalso removing the solidification substrate laminate frame 388.

The apparatus of FIGS. 16A-16E is designed for “right-side up” buildprocesses such as the one depicted in FIGS. 1A-1E. In such processes,the volume of solidifiable material held in container 44 is typicallymuch greater than in “upside down” build processes that use a shallowtray to hold the solidifiable material. In right-side up buildprocesses, the larger volume of solidifiable material 50 creates largerpressure forces against the solidification substrate laminate 298 thanwould be the case if laminate 298 were used a part of a shallow tray inan upside down build process. For example, during a leveling operation,solidifiable material 50 will exert an upward (z-axis) force against thesolidification substrate laminate 298. Once the laminate 298 is level,solidifiable material 50 will exert a dynamically varying pressureagainst the lower side of laminate 298 as solidifiable material 50 issqueezed out of the space between the exposed, upper object surface 82and the laminate 298 (FIG. 1E). As explained previously, the actuator 66may be operated to provide a level configuration force in the downwardbuild (z) axis direction to resist the upward build (z) axis forcesexerted by the solidifiable material 50 against the laminate 298. Incertain examples, the ability to provide a level configuration force isparticularly beneficial for ensuring that hydrodynamic transients in thesolidifiable material 50 to not disturb the orientation of the laminate298 relative to the x-y plane.

A solidification substrate assembly 57 with a solidification substratelaminate 298 used in lieu of film assembly 90 may be used in any of theapparatuses described herein, including those of FIGS. 6 and 10-13 inaddition to the apparatus of FIGS. 4A-4E. As discussed previously, theuse of a solidification substrate laminate 298 in place of a filmassembly 90 can be beneficially used when solidifiable material 50 isbrittle to prevent the breakage of fine structures, such as objectsupports. In preferred examples, solidification substrate assemblies 57with solidification substrate laminate 298 are used when thesolidifiable material (once solidified) has a percent elongation atbreak of greater than about three (3) percent, preferably greater thanabout five (5) percent, and even more preferably greater than about ten(10) percent. The term “percent elongation” refers to the elongation ofa sample under a tensile load using the test procedure of ASTM D-638.

The apparatus of FIGS. 16A-16F and the solidification substratelaminates of FIGS. 17A-17C may be used with any of the methods of makinga three-dimensional object from a solidifiable material describedherein, including without limitation the methods of FIGS. 7, 8A-8B, and15. Thus, the use of actuator 66 beneficially allows object peelingoperations and leveling operations to be carried out with solidificationsubstrate laminate 298 in right-side up build processes.

EXAMPLE

A 4 inch (x-axis) by 4 inch (y-axis) part is prepared using EnvisiontecE-Denstone Peach on an apparatus that is configured similarly to theapparatus of FIGS. 4A-4E but for which the solidification substrateassembly 57 is not tilted. Peeling operations are carried out by movingthe build platform 46 sufficiently downward to cause peeling andleveling (squeezing) operations are carried out by moving the buildplatform 46 upward to a distance of one layer thickness Δz from film 60.The object is built in 50 micron layers. Using the same materials andthe dimensions, the object is also built on the apparatus of FIGS. 4A-4Ewith tilting. The time required to complete a squeezing operation (i.e.,the time until the pressure measured by sensor 110 stabilizes at thereference value) is 45 seconds with the non-tilting implementation and10 seconds with tilting. The full cycle for the solidification of alayer (including dropping the build platform, performing the “squeezing”or leveling operation, curing, and peeling) is 60 seconds for thenon-tilting implementation and 12 seconds for the tiltingimplementation. Thus, the apparatuses and methods described herein arebelieved to provide significant reductions in object build timesrelative to known apparatuses.

What is claimed is:
 1. A method of making a three-dimensional objectfrom a solidifiable material having a viscosity, comprising: determiningif the viscosity exceeds a selected viscosity threshold and carrying outthe following steps if the viscosity exceeds the selected viscositythreshold: solidifying a first layer of the solidifiable material in afirst pattern corresponding to a first portion of the three-dimensionalobject to form a first solidified exposed object surface in contact witha solidification substrate assembly, wherein the first layer of thesolidifiable material is located between a build platform and thesolidification substrate assembly along a build axis, and thesolidification substrate assembly comprises one selected from a filmassembly and a solidification substrate laminate; first tilting thesolidification substrate assembly about a tilting axis in a directionaway from the build platform; moving the build platform away from thesolidification substrate assembly within a volume of the solidifiablematerial to provide a second layer of solidifiable material between thesolidified exposed object surface and the solidification substrateassembly; second tilting the solidification substrate assembly about thetilting axis in a direction toward the build platform; and solidifyingthe second layer of the solidifiable material in a second patterncorresponding to a second portion of the three-dimensional object. 2.The method of claim 1, wherein if the viscosity does not exceed theselected viscosity threshold, the method comprises: solidifying thefirst layer of the solidifiable material in the first patterncorresponding to the first portion of the three-dimensional object toform the first solidified exposed object surface in contact with asolidification substrate, wherein the first layer of the solidifiablematerial is located between the build platform and the solidificationsubstrate along the build axis; moving the build platform away from thesolidification substrate within the volume of the solidifiable materialto provide the second layer of solidifiable material between thesolidified exposed object surface and the solidification substrate; andsolidifying the second layer of the solidifiable material in the secondpattern corresponding to the second portion of the three-dimensionalobject, wherein during the method the solidification substrate is nottilted about the tilting axis.
 3. The method of claim 1, wherein afterthe completion of the step of moving the build platform away from thesolidification substrate within a volume of the solidifiable material toprovide a second layer between the solidified exposed object surface andthe solidification substrate, the step of solidifying the second layerof the solidifiable material in a second pattern is carried out afterthe expiration of a leveling wait time, and the leveling wait time is nomore than about 20 seconds.
 4. The method of claim 2, wherein after thecompletion of the step of moving the build platform away from thesolidification substrate within the volume of the solidifiable materialto provide the second layer between the solidified exposed objectsurface and the solidification substrate, the step of solidifying thesecond layer of the solidifiable material in the second pattern iscarried out after the expiration of a squeezing wait time, and thesqueezing wait time is at least about 20 seconds.
 5. The method of claim1, further comprising: applying a first level locking force to thesolidification substrate assembly during the steps of solidifying thefirst layer of the solidifiable material and solidifying the first layerof the solidifiable material.
 6. The method of claim 5, furthercomprising: applying a second level locking force to the solidificationsubstrate assembly during the step of moving the build platform awayfrom the solidification substrate.
 7. The method of claim 6, whereinfirst level locking force is greater than the second level lockingforce.
 8. The method of claim 1, wherein the step of moving the buildplatform away from the solidification substrate within a volume of thesolidifiable material to provide a second layer of solidifiable materialbetween the solidified exposed object surface and the solidificationsubstrate comprises first moving the build platform away from thesolidification substrate by a distance greater than a desired layerthickness and second moving the build platform toward the solidificationsubstrate by the difference between the distance and the desired layerthickness.
 9. The method of claim 8, wherein the three-dimensionalobject comprises a plurality of layers, and step of first moving thebuild platform away from the solidification substrate by a distancegreater than the desired layer thickness is carried out during theformation of no more than the first 30 layers of the three-dimensionalobject.
 10. The method of claim 8, wherein the distance greater than thedesired layer thickness is at least about two times the desired layerthickness.
 11. The method of claim 10, wherein the distance greater thanthe desired layer thickness is not more than about 400 times the desiredlayer thickness.
 12. The method of claim 1, wherein the solidificationsubstrate assembly includes a pattern generator, and the step ofsolidifying a first layer of the solidifiable material comprisessupplying solidification energy from the pattern generator to the firstlayer of the solidifiable material.
 13. The method of claim 1, whereinthe solidification substrate assembly comprises the solidificationsubstrate laminate, and the solidification substrate laminate comprisesa rigid or semi-rigid solidification substrate that is transparentand/or translucent.
 14. The method of claim 1, wherein thesolidification substrates assembly comprises the solidificationsubstrate laminate, and the solidification substrate laminate comprisesa film.
 15. The method of claim 1, wherein the solidification substrateassembly comprises the solidification substrate laminate, thesolidification substrate laminate comprises a resilient layer.
 16. Themethod of claim 15, wherein the resilient layer comprises a siliconeelastomer.
 17. The method of claim 1, wherein the solidificationsubstrate assembly comprises the solidification substrate laminate, andthe solidification substrate laminate comprises a polymer film formedfrom ethylenically unsaturated, halogenated monomers.
 18. The method ofclaim 17, wherein the polymer film is a fluoropolymer film.
 19. Themethod of claim 1, wherein solidification substrate assembly comprisesthe solidification substrate laminate, the solidification substratelaminate comprises a resilient layer and a polymer film formed fromethylenically unsaturated halogenated monomers bonded to the resilientlayer.
 20. The method of claim 1, wherein the selected viscositythreshold is 1500 cP at 25° C.